Evaluation of ventricle from atrium pacing therapy

ABSTRACT

Cardiac electrical heterogeneity information may be used to determine whether one or more ventricle from atrium (VfA) paced settings for VfA pacing therapy are acceptable. Cardiac electrical heterogeneity information may be generated during VfA pacing, and then evaluated to determine whether the VfA paced settings are acceptable.

The disclosure herein relates to systems and methods for use in theevaluation of ventricle from atrium (VfA) pacing therapy.

SUMMARY

The exemplary systems, methods, and interfaces described herein may beconfigured to assist a user (e.g., a physician) in evaluating a patientand/or evaluating cardiac therapy (e.g., cardiac therapy being performedon a patient during and/or after implantation of cardiac therapyapparatus). The cardiac therapy can be a ventricle from atrium (VfA)cardiac therapy, including single or multiple chamber pacing (e.g., dualor triple chamber pacing), atrioventricular synchronous pacing,asynchronous pacing, triggered pacing, cardiac resynchronization pacing,or tachycardia-related therapy. In one or more embodiments, the systems,methods, and interfaces may be described as being noninvasive. Forexample, in some embodiments, the systems, methods, and interfaces maynot need, or include, implantable devices such as leads, probes,sensors, catheters, implantable electrodes, etc. to monitor, or acquire,a plurality of cardiac signals from tissue of the patient for use inevaluating the patient and/or cardiac therapy. Instead, the systems,methods, and interfaces may use electrical measurements takennoninvasively using, e.g., a plurality of external electrodes attachedto the skin of a patient about the patient's torso.

In at least one embodiment, the exemplary systems and methods caninclude monitoring electrical activity of a patient to determineelectrical heterogeneity information associated with the patient'scardiac activity. The electrical heterogeneity information can be usedto determine whether a paced setting is acceptable for deliveringventricle from atrium (VfA) pacing therapy. In response to the pacedsetting being unacceptable, additional monitoring and determinations ofelectrical heterogeneity information can be performed using a variety ofpaced settings in order to determine which of the paced settings areacceptable.

One exemplary system may include an electrode apparatus. The electrodeapparatus can include a plurality of external electrodes to monitorelectrical activity from tissue of a patient. The exemplary system canfurther include a computing apparatus. The computing apparatus caninclude processing circuitry and can be coupled to the electrodeapparatus. The computing apparatus can be configured to monitorelectrical activity using the plurality of external electrodes. Thecomputing apparatus can be further configured to generate paced (e.g.,ventricle from atrium pacing) electrical heterogeneity information basedon the monitored electrical activity during delivery of VfA pacingtherapy at one or more VfA paced settings. The paced electricalheterogeneity information can be representative of at least one ofmechanical cardiac functionality and electrical cardiac functionality.The computing apparatus can be further configured to determine whetherone or more of the VfA paced settings for the VfA pacing therapy areacceptable based on the electrical heterogeneity information.

In at least one embodiment, an exemplary method can include monitoringelectrical activity from tissue of a patient using a plurality ofexternal electrodes. The method can further include generating pacedelectrical heterogeneity information based on the monitored electricalactivity during delivery of VfA pacing therapy at one or more VfA pacedsettings. The paced electrical heterogeneity information can berepresentative of at least one of mechanical cardiac functionality andelectrical cardiac functionality. The method can further includedetermining whether the one or more VfA paced settings associated withthe pacing therapy are acceptable based on the paced electricalheterogeneity information.

In at least one embodiment, an exemplary system can include an electrodeapparatus. The electrode apparatus can include a plurality of externalelectrodes to monitor electrical activity from tissue of a patient. Theexemplary system can include computing apparatus. The computingapparatus can include processing circuitry and can be coupled to theelectrode apparatus. The computing apparatus can be configured tomonitor electrical activity using the plurality of external electrodesduring delivery of VfA pacing therapy and to generate electricalheterogeneity information during delivery of VfA pacing therapy. Thecomputing apparatus can be further configured to determine whether a VfApaced setting for the VfA pacing therapy is acceptable based on theelectrical heterogeneity information generated from the electricalactivity using the VfA paced setting and to adjust the paced setting forthe VfA pacing therapy based on whether the VfA pacing therapy isacceptable.

The above summary is not intended to describe each embodiment or everyimplementation of the present disclosure. A more complete understandingwill become apparent and appreciated by referring to the followingdetailed description and claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an exemplary system including electrodeapparatus, display apparatus, and computing apparatus.

FIGS. 2-3 are diagrams of exemplary external electrode apparatus formeasuring torso-surface potentials.

FIG. 4 is a block diagram of an exemplary method of evaluation ofventricle from atrium pacing therapy.

FIG. 5 is a block diagram of another exemplary method of evaluation ofventricle from atrium pacing therapy.

FIG. 6 is a block diagram of another exemplary method of evaluation ofventricle from atrium pacing therapy.

FIG. 7 is a block diagram of another exemplary method of evaluation ofventricle from atrium pacing therapy.

FIG. 8 is a conceptual diagram of an illustrative cardiac therapy systemincluding an intracardiac medical device implanted in a patient's heartand a separate medical device positioned outside of the patient's heart.

FIG. 9 is an enlarged conceptual diagram of the intracardiac medicaldevice of FIG. 8 and anatomical structures of the patient's heartaccording to one example.

FIG. 10 is a perspective view of the intracardiac medical device ofFIGS. 8-9 having a distal fixation and electrode assembly that includesa distal housing-based electrode implemented as a ring electrode.

FIG. 11 is a block diagram of illustrative circuitry that may beenclosed within a housing of the intracardiac medical device of FIGS.8-10, for example, to provide the functionality and therapy describedherein.

FIG. 12 is a perspective view of an exemplary intracardiac medicaldevice according to another example for use with, e.g., the exemplarysystem of FIG. 8.

FIG. 13 is a conceptual diagram of a map of a patient's heart in astandard seventeen (17) segment view of the left ventricle showingvarious electrode implantation locations for use with, e.g., theexemplary system and devices of FIGS. 8-12.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following detailed description of illustrative embodiments,reference is made to the accompanying figures of the drawing which forma part hereof, and in which are shown, by way of illustration, specificembodiments which may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from (e.g., still falling within) the scope of the disclosurepresented hereby.

Exemplary systems and methods shall be described with reference to FIGS.1-13. It will be apparent to one skilled in the art that elements orprocesses from one embodiment may be used in combination with elementsor processes of the other embodiments, and that the possible embodimentsof such methods and systems using combinations of features set forthherein is not limited to the specific embodiments shown in the Figuresand/or described herein. Further, it will be recognized that theembodiments described herein may include many elements that are notnecessarily shown to scale. Still further, it will be recognized thattiming of the processes and the size and shape of various elementsherein may be modified but still fall within the scope of the presentdisclosure, although certain timings, one or more shapes and/or sizes,or types of elements, may be advantageous over others.

Cardiac electrical heterogeneity information can be detected orestimated in proximity of a reference location (e.g., which can be achosen location for implantation of a pacing lead or leadless device forventricle from atrium pacing cardiac therapy) using unipolarelectrocardiogram (ECG) recordings. Such electrical heterogeneityinformation may be measured and displayed, or conveyed, to an implanterby a system which acquires the ECG signals and generates various metricsof electrical heterogeneity, such as activation times (e.g.,depolarization) measured from various ECG locations.

Various exemplary systems, methods, and interfaces described herein maybe configured to use electrode apparatus including external electrodes,display apparatus, and computing apparatus to noninvasively assist auser (e.g., a physician) in the evaluation of a patient's conditionand/or ventricle from atrium (VfA) pacing cardiac therapy beingperformed on, or delivered to, a patient. The VfA pacing cardiac therapycan include pacing a left ventricle of a heart of a patient through anatrium of the heart. A leadless device or pacing lead can be extended(e.g., screwed) through the posterior basal right atrium (a locationwhich can be described as close or in near proximity to the coronarysinus (CS) ostium). The leadless device or pacing lead can beimplantable from the triangle of Koch region of the right atrium throughthe right atrial endocardium and central fibrous body to at least one ofdeliver cardiac therapy to and sense electrical activity of the leftventricle in the basal and/or septal region of the left ventricularmyocardium of a patient's heart. In this way, as an example, a leadlesspacing device (e.g., including delivering an appropriate fixationmechanism) may be thus able to sense both atrial activity as well asventricular activity in addition to atrial-ventricular (AV) synchronouspacing. Further, this VfA pacing therapy may be used for leftventricular (LV) resynchronization for heart failure patients with aleft bundle branch block (LBBB). In this case, the VfA pacing therapymay enable easier access to left ventricular endocardium withoutexposing the leadless pacing device or pacing lead to endocardial bloodpool. At the same time, the VfA pacing therapy can help engage part ofthe conduction system of the heart to potentially correct LBBB and moreeffectively resynchronize the patient's heart.

The present disclosure can include an implantable medical deviceincluding a tissue-piercing electrode and optionally a right atrialelectrode and/or a right atrial motion detector. The tissue-piercingelectrode may be implanted in the basal and/or septal region of the leftventricular myocardium of the patient's heart from the triangle of Kochregion of the right atrium through the right atrial endocardium andcentral fibrous body. In a leadless implantable medical device, thetissue-piercing electrode may leadlessly extend from a distal end regionof a housing of the device, and the right atrial electrode may beleadlessly coupled to the housing (e.g., part of or positioned on theexterior of). The right atrial motion detector may be within theimplantable medical device. In a leaded implantable medical device, oneor more of the electrodes may be coupled to the housing using animplantable lead. When the device is implanted, the electrodes may beused to sense electrical activity in one or more atria and/or ventriclesof a patient's heart. The motion detector may be used to sensemechanical activity in one or more atria and/or ventricles of thepatient's heart. In particular, the activity of the right atrium and theleft ventricle may be monitored and, optionally, the activity of theright ventricle may be monitored. The electrodes may be used to delivercardiac therapy, such as single- or multi-chamber pacing for atrialfibrillation, atrioventricular synchronous pacing for bradycardia,asynchronous pacing, triggered pacing, cardiac resynchronization pacingfor ventricular dyssynchrony, anti-tachycardia pacing, or shock therapy.Shock therapy may be initiated by the implantable medical device. Aseparate medical device, such as an extravascular ICD, which may also beimplanted, may be in operative communication with the implantablemedical device and may deliver an electrical shock in response to atrigger, such as a signaling pulse (e.g., triggering, signaling, ordistinctive electrical pulse) provided by the device.

Reference will now be made to the drawings, which depict one or moreaspects described in this disclosure. However, it will be understoodthat other aspects not depicted in the drawings fall within the scope ofthis disclosure. Like numbers used in the figures refer to likecomponents, steps, and the like. However, it will be understood that theuse of a reference character to refer to an element in a given figure isnot intended to limit the element in another figure labeled with thesame reference character. In addition, the use of different referencecharacters to refer to elements in different figures is not intended toindicate that the differently referenced elements cannot be the same orsimilar.

An exemplary system 100 including electrode apparatus 110, displayapparatus 130, and computing apparatus 140 is depicted in FIG. 1. Theelectrode apparatus 110 as shown includes a plurality of electrodesincorporated, or included, within a band wrapped around the chest, ortorso, of a patient 120. The electrode apparatus 110 is operativelycoupled to the computing apparatus 140 (e.g., through one or wiredelectrical connections, wirelessly, etc.) to provide electrical signalsfrom each of the electrodes to the computing apparatus 140 for analysis,evaluation, etc. Exemplary electrode apparatus may be described in U.S.Pat. No. 9,320,446 entitled “Bioelectric Sensor Device and Methods” andissued on Apr. 26, 2016, which is incorporated herein by reference inits entirety. Further, exemplary electrode apparatus 110 will bedescribed in more detail in reference to FIGS. 2-3.

Although not described herein, the exemplary system 100 may furtherinclude imaging apparatus. The imaging apparatus may be any type ofimaging apparatus configured to image, or provide images of, at least aportion of the patient in a noninvasive manner. For example, the imagingapparatus may not use any components or parts that may be located withinthe patient to provide images of the patient except noninvasive toolssuch as contrast solution. It is to be understood that the exemplarysystems, methods, and interfaces described herein may further useimaging apparatus to provide noninvasive assistance to a user (e.g., aphysician) to locate and position a device to deliver VfA cardiac pacingtherapy and/or to locate or select a pacing electrode or pacing vectorproximate the patient's heart for Ventricle from atrium pacing therapyin conjunction with the evaluation of Ventricle from atrium pacingtherapy.

For example, the exemplary systems, methods, and interfaces may provideimage guided navigation that may be used to navigate leads includingleadless devices, electrodes, leadless electrodes, wireless electrodes,catheters, etc., within the patient's body while also providingnoninvasive cardiac therapy evaluation including determining whether aventricle from atrium (VfA) paced setting is acceptable or determiningwhether one or more selected parameters are acceptable, such as selectedlocation information (e.g., location information for the electrodes totarget a particular location in the left ventricle). Exemplary systemsand methods that use imaging apparatus and/or electrode apparatus may bedescribed in U.S. Patent Publication No. 2014/0371832 filed on Jun. 12,2013 and entitled “Implantable Electrode Location Selection,” U.S.Patent Publication No. 2014/0371833 filed on Jun. 12, 2013 and entitled“Implantable Electrode Location Selection,” U.S. Patent Publication No.2014/0323892 filed on Mar. 27, 2014 and entitled “Systems, Methods, andInterfaces for Identifying Effective Electrodes,” U.S. PatentPublication No. 2014/0323882 filed on Mar. 27, 2014 and entitled“Systems, Methods, and Interfaces for Identifying Optical ElectricalVectors,” each of which is incorporated herein by reference in itsentirety.

Exemplary imaging apparatus may be configured to capture x-ray imagesand/or any other alternative imaging modality. For example, the imagingapparatus may be configured to capture images, or image data, usingisocentric fluoroscopy, bi-plane fluoroscopy, ultrasound, computedtomography (CT), multi-slice computed tomography (MSCT), magneticresonance imaging (MRI), high frequency ultrasound (HIFU), opticalcoherence tomography (OCT), intra-vascular ultrasound (IVUS), twodimensional (2D) ultrasound, three dimensional (3D) ultrasound, fourdimensional (4D) ultrasound, intraoperative CT, intraoperative MRI, etc.Further, it is to be understood that the imaging apparatus may beconfigured to capture a plurality of consecutive images (e.g.,continuously) to provide video frame data. In other words, a pluralityof images taken over time using the imaging apparatus may provide videoframe, or motion picture, data. Additionally, the images may also beobtained and displayed in two, three, or four dimensions. In moreadvanced forms, four-dimensional surface rendering of the heart or otherregions of the body may also be achieved by incorporating heart data orother soft tissue data from a map or from pre-operative image datacaptured by MRI, CT, or echocardiography modalities. Image datasets fromhybrid modalities, such as positron emission tomography (PET) combinedwith CT, or single photon emission computer tomography (SPECT) combinedwith CT, could also provide functional image data superimposed ontoanatomical data, e.g., to be used to navigate treatment apparatusproximate target locations (e.g., such as locations within the leftventricle, including a selected location within the high posterior basaland/or septal area of the left ventricular cavity) within the heart orother areas of interest.

Systems and/or imaging apparatus that may be used in conjunction withthe exemplary systems and method described herein are described in U.S.Pat. App. Pub. No. 2005/0008210 to Evron et al. published on Jan. 13,2005, U.S. Pat. App. Pub. No. 2006/0074285 to Zarkh et al. published onApr. 6, 2006, U.S. Pat. App. Pub. No. 2011/0112398 to Zarkh et al.published on May 12, 2011, U.S. Pat. App. Pub. No. 2013/0116739 to Bradaet al. published on May 9, 2013, U.S. Pat. No. 6,980,675 to Evron et al.issued on Dec. 27, 2005, U.S. Pat. No. 7,286,866 to Okerlund et al.issued on Oct. 23, 2007, U.S. Pat. No. 7,308,297 to Reddy et al. issuedon Dec. 11, 2011, U.S. Pat. No. 7,308,299 to Burrell et al. issued onDec. 11, 2011, U.S. Pat. No. 7,321,677 to Evron et al. issued on Jan.22, 2008, U.S. Pat. No. 7,346,381 to Okerlund et al. issued on Mar. 18,2008, U.S. Pat. No. 7,454,248 to Burrell et al. issued on Nov. 18, 2008,U.S. Pat. No. 7,499,743 to Vass et al. issued on Mar. 3, 2009, U.S. Pat.No. 7,565,190 to Okerlund et al. issued on Jul. 21, 2009, U.S. Pat. No.7,587,074 to Zarkh et al. issued on Sep. 8, 2009, U.S. Pat. No.7,599,730 to Hunter et al. issued on Oct. 6, 2009, U.S. Pat. No.7,613,500 to Vass et al. issued on Nov. 3, 2009, U.S. Pat. No. 7,742,629to Zarkh et al. issued on Jun. 22, 2010, U.S. Pat. No. 7,747,047 toOkerlund et al. issued on Jun. 29, 2010, U.S. Pat. No. 7,778,685 toEvron et al. issued on Aug. 17, 2010, U.S. Pat. No. 7,778,686 to Vass etal. issued on Aug. 17, 2010, U.S. Pat. No. 7,813,785 to Okerlund et al.issued on Oct. 12, 2010, U.S. Pat. No. 7,996,063 to Vass et al. issuedon Aug. 9, 2011, U.S. Pat. No. 8,060,185 to Hunter et al. issued on Nov.15, 2011, and U.S. Pat. No. 8,401,616 to Verard et al. issued on Mar.19, 2013, each of which is incorporated herein by reference in itsentirety.

The display apparatus 130 and the computing apparatus 140 may beconfigured to display and analyze data such as, e.g., electrical signals(e.g., electrocardiogram data), cardiac information representative of atleast one of mechanical cardiac functionality and electrical cardiacfunctionality, etc. Cardiac information may include, e.g., electricalheterogeneity information or electrical dyssynchrony information,surrogate electrical activation information or data, etc. that isgenerated using electrical signals gathered, monitored, or collected,using the electrode apparatus 110. In at least one embodiment, thecomputing apparatus 140 may be a server, a personal computer, or atablet computer. The computing apparatus 140 may be configured toreceive input from input apparatus 142 and transmit output to thedisplay apparatus 130. Further, the computing apparatus 140 may includedata storage that may allow for access to processing programs orroutines and/or one or more other types of data, e.g., for driving agraphical user interface configured to noninvasively assist a user intargeting placement of a pacing device and/or evaluating pacing therapyat that location (e.g., the location of an implantable electrode usedfor pacing, the location of pacing therapy delivered by a particularpacing vector, etc.).

The computing apparatus 140 may be operatively coupled to the inputapparatus 142 and the display apparatus 130 to, e.g., transmit data toand from each of the input apparatus 142 and the display apparatus 130.For example, the computing apparatus 140 may be electrically coupled toeach of the input apparatus 142 and the display apparatus 130 using,e.g., analog electrical connections, digital electrical connections,wireless connections, bus-based connections, network-based connections,internet-based connections, etc. As described further herein, a user mayprovide input to the input apparatus 142 to manipulate, or modify, oneor more graphical depictions displayed on the display apparatus 130 andto view and/or select one or more pieces of information related to thecardiac therapy.

Although as depicted the input apparatus 142 is a keyboard, it is to beunderstood that the input apparatus 142 may include any apparatuscapable of providing input to the computing apparatus 140 to perform thefunctionality, methods, and/or logic described herein. For example, theinput apparatus 142 may include a mouse, a trackball, a touchscreen(e.g., capacitive touchscreen, a resistive touchscreen, a multi-touchtouchscreen, etc.), etc. Likewise, the display apparatus 130 may includeany apparatus capable of displaying information to a user, such as agraphical user interface 132 including cardiac information, textualinstructions, graphical depictions of electrical activation information,graphical depictions of anatomy of a human heart, images or graphicaldepictions of the patient's heart, graphical depictions of a leadlesspacing device being positioned or placed to provide VfA pacing therapy,graphical depictions of locations of one or more electrodes, graphicaldepictions of a human torso, images or graphical depictions of thepatient's torso, graphical depictions or actual images of implantedelectrodes and/or leads, etc. Further, the display apparatus 130 mayinclude a liquid crystal display, an organic light-emitting diodescreen, a touchscreen, a cathode ray tube display, etc.

The processing programs or routines stored and/or executed by thecomputing apparatus 140 may include programs or routines forcomputational mathematics, matrix mathematics, dispersion determinations(e.g. standard deviations, variances, ranges, interquartile ranges, meanabsolute differences, average absolute deviations, etc.), filteringalgorithms, maximum value determinations, minimum value determinations,threshold determinations, moving windowing algorithms, decompositionalgorithms, compression algorithms (e.g., data compression algorithms),calibration algorithms, image construction algorithms, signal processingalgorithms (e.g., various filtering algorithms, Fourier transforms, fastFourier transforms, etc.), standardization algorithms, comparisonalgorithms, vector mathematics, or any other processing required toimplement one or more exemplary methods and/or processes describedherein. Data stored and/or used by the computing apparatus 140 mayinclude, for example, electrical signal/waveform data from the electrodeapparatus 110, dispersions signals, windowed dispersions signals, partsor portions of various signals, electrical activation times from theelectrode apparatus 110, graphics (e.g., graphical elements, icons,buttons, windows, dialogs, pull-down menus, graphic areas, graphicregions, 3D graphics, etc.), graphical user interfaces, results from oneor more processing programs or routines employed according to thedisclosure herein (e.g., electrical signals, cardiac information, etc.),or any other data that may be necessary for carrying out the one and/ormore processes or methods described herein.

In one or more embodiments, the exemplary systems, methods, andinterfaces may be implemented using one or more computer programsexecuted on programmable computers, such as computers that include, forexample, processing capabilities, data storage (e.g., volatile ornon-volatile memory and/or storage elements), input devices, and outputdevices. Program code and/or logic described herein may be applied toinput data to perform functionality described herein and generatedesired output information. The output information may be applied asinput to one or more other devices and/or methods as described herein oras would be applied in a known fashion.

The one or more programs used to implement the systems, methods, and/orinterfaces described herein may be provided using any programmablelanguage, e.g., a high-level procedural and/or object orientatedprogramming language that is suitable for communicating with a computersystem. Any such programs may, for example, be stored on any suitabledevice, e.g., a storage media, that is readable by a general or specialpurpose program running on a computer system (e.g., including processingapparatus) for configuring and operating the computer system when thesuitable device is read for performing the procedures described herein.In other words, at least in one embodiment, the exemplary systems,methods, and/or interfaces may be implemented using a computer readablestorage medium, configured with a computer program, where the storagemedium so configured causes the computer to operate in a specific andpredefined manner to perform functions described herein. Further, in atleast one embodiment, the exemplary systems, methods, and/or interfacesmay be described as being implemented by logic (e.g., object code)encoded in one or more non-transitory media that includes code forexecution and, when executed by a processor, is operable to performoperations such as the methods, processes, and/or functionalitydescribed herein.

The computing apparatus 140 may be, for example, any fixed or mobilecomputer system (e.g., a controller, a microcontroller, a personalcomputer, minicomputer, tablet computer, etc.) and may be generallydescribed as including processing circuitry. The exact configuration ofthe computing apparatus 140 is not limiting, and essentially any devicecapable of providing suitable computing capabilities and controlcapabilities (e.g., graphics processing, etc.) may be used. As describedherein, a digital file may be any medium (e.g., volatile or non-volatilememory, a CD-ROM, a punch card, magnetic recordable medium such as adisk or tape, etc.) containing digital bits (e.g., encoded in binary,trinary, etc.) that may be readable and/or writeable by computingapparatus 140 described herein. Also, as described herein, a file inuser-readable format may be any representation of data (e.g., ASCIItext, binary numbers, hexadecimal numbers, decimal numbers, graphically,etc.) presentable on any medium (e.g., paper, a display, etc.) readableand/or understandable by a user.

In view of the above, it will be readily apparent that the functionalityas described in one or more embodiments according to the presentdisclosure may be implemented in any manner as would be known to oneskilled in the art. As such, the computer language, the computer system,or any other software/hardware which is to be used to implement theprocesses described herein shall not be limiting on the scope of thesystems, processes or programs (e.g., the functionality provided by suchsystems, processes or programs) described herein.

Electrical activation times of the patient's heart may be useful toevaluate a patient's cardiac condition and/or ventricle from atrium(VfA) cardiac therapy being delivered to a patient. Surrogate electricalactivation information or data of one or more regions of a patient'sheart may be monitored, or determined, using electrode apparatus 110 asshown in FIG. 1 and in FIG. 2-3. The exemplary electrode apparatus 110may be configured to measure body-surface potentials of a patient 120and, more particularly, torso-surface potentials of a patient 120. Asshown in FIG. 2, the exemplary electrode apparatus 110 may include aset, or array, of electrodes 112, a strap 113, and interface/amplifiercircuitry 116. In at least one embodiment, a portion of the set ofelectrodes may be used wherein the portion corresponds to a particularlocation on the patient's heart. The electrodes 112 may be attached, orcoupled, to the strap 113 and the strap 113 may be configured to bewrapped around the torso of a patient 120 such that the electrodes 112surround the patient's heart. As further illustrated, the electrodes 112may be positioned around the circumference of a patient 120, includingthe posterior, lateral, posterolateral, anterolateral, and anteriorlocations of the torso of a patient 120.

Further, the electrodes 112 may be electrically connected tointerface/amplifier circuitry 116 via wired connection 118. Theinterface/amplifier circuitry 116 may be configured to amplify thesignals from the electrodes 112 and provide the signals to the computingapparatus 140. Other exemplary systems may use a wireless connection totransmit the signals sensed by electrodes 112 to the interface/amplifiercircuitry 116 and, in turn, the computing apparatus 140, e.g., aschannels of data. For example, the interface/amplifier circuitry 116 maybe electrically coupled to each of the computing apparatus 140 and thedisplay apparatus 130 using, e.g., analog electrical connections,digital electrical connections, wireless connections, bus-basedconnections, network-based connections, internet-based connections, etc.

Although in the example of FIG. 2 the electrode apparatus 110 includes astrap 113, in other examples any of a variety of mechanisms, e.g., tapeor adhesives, may be employed to aid in the spacing and placement ofelectrodes 112. In some examples, the strap 113 may include an elasticband, strip of tape, or cloth. In other examples, the electrodes 112 maybe placed individually on the torso of a patient 120. Further, in otherexamples, electrodes 112 (e.g., arranged in an array) may be part of, orlocated within, patches, vests, and/or other manners of securing theelectrodes 112 to the torso of the patient 120.

The electrodes 112 may be configured to surround the heart of thepatient 120 and record, or monitor, the electrical signals associatedwith the depolarization and repolarization of the heart after thesignals have propagated through the torso of a patient 120. Each of theelectrodes 112 may be used in a unipolar configuration to sense thetorso-surface potentials that reflect the cardiac signals. Theinterface/amplifier circuitry 116 may also be coupled to a return orindifferent electrode (not shown) that may be used in combination witheach electrode 112 for unipolar sensing. In some examples, there may beabout 12 to about 50 electrodes 112 spatially distributed around thetorso of patient. Other configurations may have more or fewer electrodes112.

The computing apparatus 140 may record and analyze the electricalactivity (e.g., torso-surface potential signals) sensed by electrodes112 and amplified/conditioned by the interface/amplifier circuitry 116.The computing apparatus 140 may be configured to analyze the signalsfrom the electrodes 112 to provide as anterior and posterior electrodesignals and surrogate cardiac electrical activation times, e.g.,representative of actual, or local, electrical activation times of oneor more regions of the patient's heart as will be further describedherein. The computing apparatus 140 may be configured to analyze thesignals from the electrodes 112 to provide as anterior-septal electrodesignals and surrogate cardiac electrical activation times, e.g.,representative of actual, or local, electrical activation times of oneor more anterior-septal regions of the patient's heart, as will befurther described herein, e.g., for use in evaluation of VfA pacingtherapy. Further, the electrical signals measured at the left anteriorsurface location of a patient's torso may be representative, orsurrogates, of electrical signals of the left anterior left ventricleregion of the patient's heart, electrical signals measured at the leftlateral surface location of a patient's torso may be representative, orsurrogates, of electrical signals of the left lateral left ventricleregion of the patient's heart, electrical signals measured at the leftposterolateral surface location of a patient's torso may berepresentative, or surrogates, of electrical signals of theposterolateral left ventricle region of the patient's heart, andelectrical signals measured at the posterior surface location of apatient's torso may be representative, or surrogates, of electricalsignals of the posterior left ventricle region of the patient's heart.In one or more embodiments, measurement of activation times can beperformed by measuring the period of time between an onset of cardiacdepolarization (e.g., onset of QRS complex) and an appropriate fiducialpoint such as, e.g., a peak value, a minimum value, a minimum slope, amaximum slope, a zero crossing, a threshold crossing, etc.

Additionally, the computing apparatus 140 may be configured to providegraphical user interfaces depicting the surrogate electrical activationtimes obtained using the electrode apparatus 110. Exemplary systems,methods, and/or interfaces may noninvasively use the electricalinformation collected using the electrode apparatus 110 to evaluate apatient's cardiac condition and/or ventricle from atrium pacing therapybeing delivered to the patient.

FIG. 3 illustrates another exemplary electrode apparatus 110 thatincludes a plurality of electrodes 112 configured to surround the heartof the patient 120 and record, or monitor, the electrical signalsassociated with the depolarization and repolarization of the heart afterthe signals have propagated through the torso of the patient 120. Theelectrode apparatus 110 may include a vest 114 upon which the pluralityof electrodes 112 may be attached, or to which the electrodes 112 may becoupled. In at least one embodiment, the plurality, or array, ofelectrodes 112 may be used to collect electrical information such as,e.g., surrogate electrical activation times. Similar to the electrodeapparatus 110 of FIG. 2, the electrode apparatus 110 of FIG. 3 mayinclude interface/amplifier circuitry 116 electrically coupled to eachof the electrodes 112 through a wired connection 118 and be configuredto transmit signals from the electrodes 112 to computing apparatus 140.As illustrated, the electrodes 112 may be distributed over the torso ofa patient 120, including, for example, the anterior, lateral,posterolateral, anterolateral, and posterior surfaces of the torso ofthe patient 120.

The vest 114 may be formed of fabric with the electrodes 112 attached tothe fabric. The vest 114 may be configured to maintain the position andspacing of electrodes 112 on the torso of the patient 120. Further, thevest 114 may be marked to assist in determining the location of theelectrodes 112 on the surface of the torso of the patient 120. In one ormore embodiments, the vest 114 may include 17 or more anteriorelectrodes positionable proximate the anterior torso of the patient, and39 or more posterior electrodes positionable proximate the anteriortorso of the patient. In some examples, there may be about 25 electrodes112 to about 256 electrodes 112 distributed around the torso of thepatient 120, though other configurations may have more or lesselectrodes 112.

As described herein, the electrode apparatus 110 may be configured tomeasure electrical information (e.g., electrical signals) representingdifferent regions of a patient's heart. For example, activation times ofdifferent regions of a patient's heart can be approximated from surfaceelectrocardiogram (ECG) activation times measured using surfaceelectrodes in proximity to surface areas corresponding to the differentregions of the patient's heart. In at least one example, activationtimes of the anterior-septal region of a patient's heart can beapproximated from surface ECG activation times measured using surfaceelectrodes in proximity to surface areas corresponding to theanterior-septal region of the patient's heart. That is, a portion of theset of electrodes 112, and not the entire set, can be used to generateactivation times corresponding to a particular location of the patient'sheart that the portion of the set of electrodes corresponds to.

The exemplary systems, methods, and interfaces may be used to providenoninvasive assistance to a user in the evaluation of a patient'scardiac health or status, and/or the evaluation of cardiac therapy suchas ventricle from atrium (VfA) pacing therapy by use of the electrodeapparatus 110 (e.g., cardiac therapy being presently-delivered to apatient during implantation or after implantation). Further, theexemplary systems, methods, and interfaces may be used to assist a userin the configuration of the cardiac therapy, such as VfA pacing therapy,being delivered to a patient.

VfA pacing can be described as providing a synchronized homogeneousactivation of ventricles of the heart. As an example, patients withatrial-ventricular (AV) block or prolonged AV timings that can lead toheart failure who have otherwise intact (e.g., normal) QRS can benefitfrom VfA pacing therapy. In addition, as an example, VfA pacing mayprovide beneficial activation for heart failure patients with intrinsicventricular conduction disorders. Further, proper placement of VfApacing can provide optimal activation of the ventricles for suchpatients. Further, left ventricular (LV) resynchronization for heartfailure patients with left bundle branch block (LBBB) may find that VfApacing enables easier access to left ventricular endocardium withoutexposing the leadless device or lead to endocardial blood pool. At thesame time, in that example, this can help engage part of the conductionsystem to potentially correct LBBB and effectively resynchronize thepatient.

An exemplary method 440 of evaluation of VfA pacing is illustrated inFIG. 4. The method 440 can include monitoring electrical activity usinga plurality of external electrodes 442, such as electrodes 112 describedherein with reference to FIGS. 1-3. The electrical activity can bemonitored by a plurality of electrodes during VfA pacing therapy or inthe absence of VfA pacing therapy. The monitored electrical activity canbe used to evaluate VfA pacing therapy to a patient using, e.g., theexemplary system described herein with respect to FIGS. 1-3. Theelectrical activity monitored using the ECG belt described above can beused to evaluate at least one paced setting of the VfA pacing therapy onthe heart. As an example, a paced setting can be any one parameter or acombination of parameters including, but not limited to, electrodeposition, pacing polarity, pacing output, pacing pulsewidth, timing atwhich VfA pacing is delivered relative to atrial (A) timing, pacingrate, etc. Further, as an example, the location of the leadless deviceor a pacing lead can include a location in the left ventricle, accessedthrough the right atrium within, or in close proximity to, the highposterior basal and/or septal (HPBS) area of the left ventricularcavity. Moreover, pacing of, or in close proximity to, the HPBS area canbe selective (e.g., involving stimulation of a particular area of theHPBS alone) or non-selective (e.g., combined pacing at the location ofthe HPBS and other atrial and/or ventricular septum areas).

Further, body-surface isochronal maps of ventricular activation can beconstructed using the monitored electrical activity during VfA pacingtherapy or in the absence of VfA pacing therapy. The monitoredelectrical activity and/or the map of ventricular activation can be usedto generate electrical heterogeneity information. The electricalheterogeneity information can include determining metrics of electricalheterogeneity. The metrics of electrical heterogeneity can include ametric of standard deviation of activation times (SDAT) of electrodes ona left side of a torso of the patient and/or a metric of mean leftventricular activation time (LVAT) of electrodes on the left side of thetorso of the patient. A metric of LVAT may be determined from electrodeson both the anterior and posterior surfaces, which are more proximal tothe left ventricle. The metrics of electrical heterogeneity informationcan include a metric of mean right ventricular activation time (RVAT) ofelectrodes on the right side of the torso of the patient. A metric ofRVAT may be determined from electrodes on both the anterior andposterior surfaces which are more proximal to the right ventricle. Themetrics of electrical heterogeneity can include a metric of mean totalactivation time (mTAT) taken from a plurality of electrode signals fromboth sides of the torso of the patient, or it may include other metrics(e.g., standard deviation, interquartile deviations, a differencebetween a latest activation time and earliest activation time)reflecting a range or dispersion of activation times on a plurality ofelectrodes located on the right side of the patient torso or left sideof the patient torso, or combining both right and left sides of thepatient torso. The metrics of electrical heterogeneity information caninclude a metric of anterior-septal activation times (ASAT) ofelectrodes on the torso in close proximity to the anterior-septalportion of the heart.

Thus, the method 440 can include generating electrical heterogeneityinformation during delivery of VfA pacing therapy at one or more VfApaced settings 444. The electrical heterogeneity information can begenerated using metrics of electrical heterogeneity. As an example, themetrics of electrical heterogeneity can include at least one of an SDAT,an LVAT, an RVAT, an mTAT, and an ASAT. In at least one embodiment, onlyASAT may be determined and further used by method 440, and/or ASAT maybe more heavily weighted than other values.

The method 440 can include determining whether one or more pacedsettings associated with the VfA pacing therapy are acceptable 446. Apaced setting can include a plurality of pacing parameters. Theplurality of pacing parameters can be acceptable if the patient'scardiac condition improves, if the VfA pacing therapy is effectivelycapturing a desired portion of the left ventricle (e.g., the highposterior basal and/or septal area), and/or if a metric of electricalheterogeneity improves by a certain threshold compared to a baselinerhythm or therapy. In at least one embodiment, the determination ofwhether the paced setting is acceptable can be based on at least onemetric of electrical heterogeneity generated from electrical activityduring VfA pacing (and also, in some embodiments, during nativeconduction, or in the absence of VfA pacing). The at least one metriccan include at least one of an SDAT, an LVAT, an RVAT, an mTAT, an ASAT.

Further, the plurality of pacing parameters can be acceptable if ametric of electrical heterogeneity is greater than or less than aparticular threshold, and/or if the location of the pacing therapy toexcite the left ventricle causes a particular pattern of excitation ofthe muscle fibers in the heart. In addition, the plurality of pacingparameters can be acceptable if a metric of electrical heterogeneityindicates a correction of a left bundle branch block (LBBB), and/or if ametric of electrical heterogeneity indicates a complete engagement of aPurkinje system, etc. As an example, a metric of electricalheterogeneity of an ASAT less than or equal to a threshold (e.g., athreshold of 30 ms) and an LVAT less than or equal to a threshold (e.g.,a threshold of 30 ms) can indicate a correction of an LBBB, and thus,the paced setting is acceptable. As an example, a metric of electricalheterogeneity of an RVAT less than or equal to a threshold (e.g., athreshold of 30 ms), an ASAT less than or equal to a threshold (e.g., athreshold of 30 ms), and an LVAT less than or equal to a threshold(e.g., a threshold of 30 ms) can indicate a complete engagement of thePurkinje system, and thus the paced setting is acceptable.

The paced setting can be determined to be acceptable in response to theVfA pacing therapy using the paced setting being optimal, beingbeneficial, being indicative of complete engagement of patient's nativecardiac conduction system, being indicative of correction of aventricular conduction disorder (e.g., left bundle branch block), etc. Apaced setting can include at least one of a pacing electrode position(including at least one of a depth, an angle, an amount of turn for ascrew-based fixation mechanism, etc.), a voltage, a pulse width, anintensity, a pacing polarity, a pacing vector, a pacing waveform, atiming of the pacing delivered relative to an intrinsic or paced atrialevent or relative to the intrinsic His bundle potential, and/or a pacinglocation, etc. A pacing vector can include any two or more pacingelectrodes such as, e.g., a tip electrode to a can electrode, a tipelectrode to a ring electrode etc., that are used to deliver the VfApacing therapy, etc. The pacing location can refer to the location ofany of the one or more pacing electrodes that are positioned using alead, a leadless device, and/or any device or apparatus configured todeliver VfA, as will be further described in association with FIGS.8-12.

The method 440 can include adjusting a paced setting for VfA pacingtherapy 448. In at least one embodiment, the paced setting can beadjusted in response to the paced setting being unacceptable. In atleast one embodiment, the paced setting can be adjusted in response tothe paced setting being within an acceptable range but in order todetermine whether the paced setting can be at a position within theacceptable range that is more beneficial, more useful, more functional,etc. for the VfA pacing therapy. As an example, when the paced settingis a location that the VfA pacing therapy is administered within apatient, the paced setting (e.g., location, depth of penetration ofhelical electrode, angle of helical electrode, etc.) can be adjusteduntil the VfA pacing therapy results in a metric of electricalheterogeneity that is above or below a threshold metric of electricalheterogeneity. That is, the paced setting can be adjusted to assist inplacement of a lead, leadless device, and/or other electrical device toadminister the VfA pacing therapy. In another embodiment, the pacedsetting could be adjusted to find the most optimal metric of electricalheterogeneity.

For example, pacing of the left ventricle can utilize a pacing electrodethat includes anywhere from an approximately 4 millimeter (mm) longhelix to an approximately 12 mm long helix, and the exemplary method 440may be used to gradually titrate navigating the electrode up to a 4 mmdepth, or some other particular depth. In at least one example, thepacing electrode includes an 8 mm long helix. More specifically, thepacing electrode may be partially screwed into or through a posteriorbasal area of the right atrium. Further, the pacing electrode may passthrough the right atrium and be screwed into, attached to, or broughtinto close proximity to a location in the left ventricle. This locationof the left ventricle can include a high posterior basal and/or septalarea of the left ventricle where the VfA pacing may be performed,electrical activity may be monitored 442 during such VfA pacing,electrical heterogeneity information may be generated 444, and it may bedetermined whether the pacing setting, which in this case, may be anelectrode location including depth and/or angle, is acceptable 446.Next, the paced setting, which in this case may be a location includingdepth and/or angle, may be adjusted 448. Thus, the pacing electrode maybe screwed in, or through, the right atrium to be positioned in closeproximity to or deeper within tissue in order to gain access to the leftventricle, and the method 440 may reiterate or be repeated until suchdesired location is achieved. In other words, the exemplary method 440may indicate to a doctor to gradually slow down turning of the helixelectrode through the right atrium allowing it to gain access to theleft ventricle and be in close proximity to a portion of the leftventricle (e.g., the high posterior basal and/or septal area).

Further, in one or more embodiments, a determination of whether thepaced setting is acceptable can be based on a particular metric ofelectrical heterogeneity using an ECG belt. For example, when a pacedsetting is associated with a first metric value of electricalheterogeneity, an indication (e.g., a display, a prompt, etc.) to turn apacing electrode helix a particular number of turns can be made (e.g.,to adjust the depth and/or angle of implant of the pacing electrodehelix). In response to the paced setting being associated with a secondmetric value of electrical heterogeneity, an indication to stop turningthe pacing electrode helix can be made. Furthermore, based on a metricof electrical heterogeneity, an indication of how many more turns of thepacing electrode helix can be indicated to assist in determining howmuch further to go with the pacing electrode helix. These indicationscan be displayed on a GUI of a monitor to assist in adjusting the pacedsetting and/or be on any number of display and/or notification devices.

In at least one example, the paced setting can be adjusted at intervalsthat correlate with a change in the metric of electrical heterogeneityuntil the metric of electrical heterogeneity is at or proximate aparticular metric value. For instance, the adjusting of the pacedsetting can cause the metric of electrical heterogeneity to approach aparticular threshold metric of electrical heterogeneity and, as themetric approaches the particular threshold, the rate at which the pacedsetting is adjusted can be slowed down. Put another way, as the metricof electrical heterogeneity is further from the particular thresholdmetric, the paced setting can be adjusted more quickly and as the metricof electrical heterogeneity gets closer to the particular thresholdmetric, the paced setting can be adjusted more slowly until the metricof electrical heterogeneity is at the particular threshold metric.

In at least one example, the paced setting (e.g., location includingdepth and/or angle) can be adjusted until the VfA pacing therapy resultsin a correction of bundle branch block (BBB) (or, more specifically,left BBB (LBBB). BBB can refer to a condition in which a delay and/orobstruction along a pathway that the electrical activity of the heart ofthe patient travels in order for the heart to properly beat. The delayand/or blockage may occur on the pathway that sends electrical impulsesto the left or right side of the ventricles of the heart. The pacedsetting can be adjusted until the delay and/or blockage along thepathway is remedied, which can be indicated by a change in the metric ofelectrical heterogeneity, the metric of electrical heterogeneity beingabove or below a particular threshold, and/or any number of electricalinformation that may indicate that the BBB has been corrected.

In at least one example, the paced setting can be adjusted until themetric of electrical heterogeneity indicating a delay and/or blockage ofBBB reaches a particular threshold metric. The metric of electricalheterogeneity being at the particular threshold metric can indicate theBBB has been corrected. The paced setting can be adjusted at a greaterrate while the metric of electrical heterogeneity is further from theparticular threshold metric and adjusted at a slower rate as the metricof electrical heterogeneity gets closer to the particular thresholdmetric. More specifically in response to at least one metric ofelectrical heterogeneity such as ASAT and LVAT being below a threshold,such as below 30 milliseconds (ms) for each of ASAT and LVAT, anindication of a correction of LBBB can be determined.

In at least one embodiment, the electrical heterogeneity information canbe generated while delivering VfA pacing cardiac therapy using aselected first paced setting. In response to the selected first pacedsetting being determined to be an unacceptable paced setting, a selectedsecond paced setting can be used. As an example, the first paced settingcan include a first location of an electrode in the left ventricle, byway of going through the right atrium a first distance. In response tothe first location not being indicated as an acceptable locationevaluated at one or more pacing voltages, polarities, or timings, asecond location within the left ventricle, associated with a seconddistance through the right atrium, can be used for delivering the VfApacing therapy.

Lead placement at a site at, or in close proximity to, a particularlocation in the left ventricle (e.g., basal and/or septal area of theleft ventricular myocardium) can be determined using the methoddescribed above. In at least one example, the method can be performedduring implant placement. A decision-making process to determine whetherto use the tested location (e.g., a first location) or to try for anadditional location (e.g., a second location) for better results couldbe based on an automated system. As an example, parameters can be set toindicate whether the location is acceptable and when those parametersare met, the system automatically accepts the paced settings (e.g.,location for VfA pacing using a lead or leadless device). In response toa determination that the VfA pacing therapy is not acceptable (e.g., theVfA paced setting used to deliver the VfA pacing therapy), the VfA pacedsetting can be changed. In response to changing the paced setting, adetermination of whether the changed VfA paced setting for the VfApacing therapy is acceptable based on the electrical heterogeneityinformation generated from the electrical activity using the pluralityof external electrodes during delivery of VfA pacing therapy using thechanged VfA paced setting can be performed. In at least one example, thedata from the metrics of electrical heterogeneity can be provided to aclinician and the clinician can make the decision whether to accept thepaced setting (e.g., a location for VfA pacing using a lead or leadlessdevice).

In at least one embodiment, a metric of electrical heterogeneity used todetermine whether a paced setting is acceptable can be used to compareVfA pacing therapy to cardiac resynchronization therapy (CRT). A metricof electrical heterogeneity while performing CRT can be generated. Then,as an example, the metric of electrical heterogeneity for CRT can becompared to the metric of electrical heterogeneity for VfA pacing.

FIG. 5 is a detailed block diagram of another exemplary method 550 ofevaluating VfA pacing therapy. The method 550 can include monitoringelectrical activity using a plurality of external electrodes 552, suchas electrodes 112 described herein with reference to FIGS. 1-3. Theelectrical activity can be monitored by a plurality of electrodes duringVfA pacing therapy or in the absence of VfA pacing therapy. Themonitored electrical activity can be used to evaluate VfA pacing therapyto a patient using, e.g., the exemplary system described herein withrespect to FIGS. 1-3. The electrical activity monitored using the ECGbelt described above can be used to evaluate at least one paced settingof the VfA pacing therapy on the heart.

The method 550 can include generating baseline electrical heterogeneityinformation (EHI) 554. The baseline EHI can be generated in the absenceof VfA pacing therapy. That is, the baseline EHI can be generated fromelectrical activity that is monitored in the absence of the VfA pacingtherapy. The baseline EHI can include a baseline metric of electricalheterogeneity. A baseline metric can refer to a metric generated duringnative AV conduction in the absence of VfA pacing therapy to a patientor a metric generated during previous VfA pacing therapy using differentsettings or parameters or a metric generated during other cardiac pacing(e.g., more conventional cardiac pacing such as right ventricularpacing). The baseline metric can include at least one of an SDAT, anLVAT, an RVAT, an mTAT, and an ASAT. In one embodiment, an ASAT onlybaseline metric can be used.

The method 550 can include generating paced electrical heterogeneityinformation (EHI) during delivery of VfA pacing therapy 556. The pacedEHI can include a therapy metric of electrical heterogeneity. A therapymetric can refer to a metric generated while delivering VfA pacingtherapy to a patient. The therapy metric can include at least one of anSDAT, an LVAT, an RVAT, an mTAT, and an ASAT.

The method 550 can include comparing the baseline EHI to the paced EHI558. Comparing the baseline EHI to the paced EHI can include comparing abaseline metric of electrical heterogeneity of the baseline EHI to atherapy metric of electrical heterogeneity of the paced EHI. As anexample, a baseline SDAT can be compared to a therapy SDAT, a baselineLVAT can be compared to a therapy LVAT, a baseline RVAT can be comparedto a therapy RVAT, a baseline mTAT can be compared to a therapy mTAT,and a baseline ASAT can be compared to a therapy ASAT. Further, forexample, in at least one embodiment, a relative percentage differencebetween one or more metrics of EH generated during delivery of VfApacing therapy and one or more baseline metrics of EH (either in theabsence of delivery of VfA pacing therapy or during previous settings ofVfA pacing therapy) may be compared to a threshold percentage. In oneembodiment, an baseline ASAT metric of EH can be compared to a pacedASAT metric of EH.

The method 550 can include determining whether a paced setting for theVfA pacing therapy is acceptable based on the comparison 560. A selectedpaced setting can be used to deliver the VfA pacing therapy andelectrical heterogeneity information can be generated while using thepaced setting. The determination of whether the paced setting isacceptable can be based on the comparison of the baseline EHI to atherapy EHI while using the paced setting. As an example, VfA pacingusing the paced setting may be considered acceptable if the relativepercentage difference (e.g., reduction) in EH with pacing compared to EHwithout pacing is less than or equal or greater than or equal to apercentage threshold. More specifically, in at least one embodiment, theone or more metrics of EH may be SDAT, LVAT, RVAT, mTAT, ASAT, or anycombination thereof, and the selected percentage threshold may bebetween about 1% to about 15%. In at least one embodiment, the selectedpercentage threshold for the absolute relative difference (e.g.,reduction) in EH with VfA pacing compared to without VfA pacing is 5%.In one or more other embodiments the selected percentage may be lessthan or equal to or greater than or equal to 2%, less than or equal toor greater than or equal to 3%, less than or equal to or greater than orequal to 6%, less than or equal to or greater than or equal to 9%, lessthan or equal to or greater than or equal to 10%, less than or equal toor greater than or equal to 15%, etc.

In at least one embodiment, as an example, the threshold percentage canbe 5% for each of SDAT and LVAT. Thus, in this embodiment, if the change(e.g., reduction) in SDAT from baseline conduction to VfA pacing therapyis greater than or equal to 5% and the change (e.g., reduction) in LVATfrom baseline conduction to VfA pacing therapy is greater than or equalto 5%, it may be determined that the VfA pacing therapy is acceptable.Conversely, if the change (e.g., relative reduction) in SDAT frombaseline conduction to VfA pacing therapy is less than 5% and the change(e.g., relative reduction) in LVAT from baseline conduction to VfApacing therapy is less than 5%, it may be determined that the VfA pacingtherapy is unacceptable. The threshold reduction of metrics ofelectrical heterogeneity (e.g., reduction of electrical dyssynchrony)from baseline to pacing can indicate an improvement in resynchronizationof the patient's heart.

Additionally, although the comparison of EH metrics to thresholds andthe comparison of the percentage difference between EH metrics generatedduring delivery of VfA pacing therapy and EH baseline metrics aredescribed separately, it is to be understood that each process may beused by itself or together to determine whether the Vfa pacing therapyis acceptable (or more specifically, whether one or more parameters ofthe VfA pacing therapy are acceptable).

The method 550 can further include adjusting the paced setting for theVfA pacing therapy 562. The adjustment of the paced setting can beperformed in response to the determination 560 that the paced settingfor the VfA pacing therapy is acceptable. In this example, the pacedsetting could be adjusted to find a paced setting that is moreacceptable than the already accepted paced setting. That is, a pacedsetting may be acceptable due to corresponding therapy EHI being withinan acceptable range but adjusting to another paced setting may result intherapy EHI that is closer to a particular portion of the range that ismore acceptable. Further, in at least one embodiment, the adjustment ofthe paced setting can be performed in response to the determination 560that the paced setting for the VfA pacing therapy is unacceptable.

In response to the paced setting being adjusted, the process can repeat,starting with monitoring electrical activity 552, generating baselineEHI 554, generating paced EHI 556, comparing baseline EHI to therapy EHI558, and determining whether the paced setting is acceptable 560. Thisiterative process can repeat until either a paced setting is determinedto be acceptable or the paced setting is within acceptable ranges, etc.As an example, where the paced setting is one of location, the location(including at least one of depth and angle) of an implantable electrodefor delivering VfA pacing therapy can be adjusted, and this processrepeated, until the therapy EHI associated with a particular location ofthe implantable electrode is acceptable.

FIG. 6 is a block diagram of another exemplary method 446-1 ofevaluation of ventricle from atrium pacing therapy. The method 446-1 canbe described as one exemplary embodiment of method step 446 in method440 described in association with FIG. 4. That is, determining whetherpaced setting(s) for the VfA pacing therapy is acceptable 446 of method440 can include the steps of method 446-1 in FIG. 6. The method 446-1can include determining whether an anterior-septal activation time(ASAT) value is equal to or less than an ASAT threshold 664. Ananterior-septal region may be described as referring to a location infront of the interventricular septum, which refers to the curvedslanting wall that separates the right and left ventricles of the heartand is composed of a muscular lower part and a thinner more membranousupper part. The ASAT value can be a value generated from electricalactivity gathered by external electrodes in close proximity to theanterior-septal region or whose electrical activity corresponds to theanterior-septal region. In at least one example, the ASAT threshold canbe 30 ms. The ASAT threshold can be greater than or equal to about 20ms, greater than or equal to about 30 ms, greater than or equal to about40 ms, greater than or equal to about 50 ms, greater than or equal toabout 60 ms, etc. Also, the ASAT threshold can be less than or equal toabout 25 ms, less than or equal to about 35 ms, less than or equal toabout 45 ms, less than or equal to about 55 ms, etc.

The method 446-1 can include determining whether a left ventricularactivation time (LVAT) value is below an LVAT threshold 666. The LVATvalue can be a value generated from electrical activity gathered byexternal electrodes in close proximity to the left ventricular region orwhose electrical activity corresponds to the left ventricular region. Inat least one example, the LVAT threshold can be 30 ms. The LVATthreshold can be greater than or equal to about 20 ms, greater than orequal to about 30 ms, greater than or equal to about 40 ms, greater thanor equal to about 50 ms, greater than or equal to about 60 ms, etc.Also, the LVAT threshold can be less than or equal to about 25 ms, lessthan or equal to about 35 ms, less than or equal to about 45 ms, lessthan or equal to about 55 ms, etc.

The method 446-1 can include determining that the paced setting appearsto correct a left bundle branch block (LBBB) in response to the ASATvalue and the LVAT value being below their respective thresholds 668. Asan example, the ASAT value can be less than or equal to a threshold of30 ms and the LVAT value can be less than or equal to a threshold of 30ms in order to indicate that the LBBB has been corrected. In at leastone example, the ASAT threshold can be greater than or equal to 20 msand the LVAT threshold can be greater than or equal to 20 ms, the ASATthreshold can be greater than or equal to 25 ms and the LVAT thresholdcan be greater than or equal to 25 ms, the ASAT threshold can be greaterthan or equal to 20 ms and the LVAT threshold can be greater than orequal to 30 ms, the ASAT threshold can be greater than or equal to 30 msand the LVAT threshold can be greater than or equal to 20 ms, and soforth for any combination of ASAT and LVAT thresholds. Also, the ASATthreshold can be less than or equal to 20 ms and the LVAT threshold canbe less than or equal to 20 ms, the ASAT threshold can be less than orequal to 25 ms and the LVAT threshold can be less than or equal to 25ms, the ASAT threshold can be less than or equal to 20 ms and the LVATthreshold can be less than or equal to 30 ms, the ASAT threshold can beless than or equal to 30 ms and the LVAT threshold can be less than orequal to 20 ms, and so forth for any combination of ASAT and LVATthresholds. Thus, if during VfA pacing, the ASAT is less than or equalto a ASAT threshold and the LVAT is less than equal to an LVATthreshold, it may be determined that the VfA pacing therapy iscorrecting the LBBB.

FIG. 7 is a block diagram of another exemplary method 446-2 ofevaluation of ventricle from atrium pacing therapy. The method 446-2 canbe described as one exemplary embodiment of method step 446 in method440 described in association with FIG. 4. That is, determining whetherpaced setting(s) for the VfA pacing therapy is acceptable 446 of method440 can include the steps of method 446-2 in FIG. 6. The method 446-2can include determining whether a right ventricular activation time(RVAT) value is equal to or less than an RVAT threshold 771. The RVATvalue can be a value generated from electrical activity gathered byexternal electrodes in close proximity to the right ventricular regionor whose electrical activity corresponds to the right ventricularregion. In at least one example, the RVAT threshold can be 30 ms. In atleast one example, the RVAT threshold can be 30 ms. The RVAT thresholdcan be greater than or equal to about 20 ms, greater than or equal toabout 30 ms, greater than or equal to about 40 ms, greater than or equalto about 50 ms, greater than or equal to about 60 ms, etc. Also, theRVAT threshold can be less than or equal to about 25 ms, less than orequal to about 35 ms, less than or equal to about 45 ms, less than orequal to about 55 ms, etc.

The method 446-2 can include determining whether an anterior-septalactivation time (ASAT) value is equal to or less than an ASAT threshold773. An anterior-septal region can refer to a location in front of theinterventricular septum, which refers to the curved slanting wall thatseparates the right and left ventricles of the heart and is composed ofa muscular lower part and a thinner more membranous upper part. The ASATvalue can be a value generated from electrical activity gathered byexternal electrodes in close proximity to the anterior-septal region orwhose electrical activity corresponds to the anterior-septal region. Inat least one example, the ASAT threshold can be 30 ms. The ASATthreshold can be greater than or equal to about 20 ms, greater than orequal to about 30 ms, greater than or equal to about 40 ms, greater thanor equal to about 50 ms, greater than or equal to about 60 ms, etc.Also, the ASAT threshold can be less than or equal to about 25 ms, lessthan or equal to about 35 ms, less than or equal to about 45 ms, lessthan or equal to about 55 ms, etc.

The method 446-2 can include determining whether a left ventricularactivation time (LVAT) value is equal to or less than an LVAT threshold775. The LVAT value can be a value generated from electrical activitygathered by external electrodes in close proximity to the rightventricular region or whose electrical activity corresponds to the rightventricular region. In at least one example, the LVAT threshold can be30 ms. The LVAT threshold can be greater than or equal to about 20 ms,greater than or equal to about 30 ms, greater than or equal to about 40ms, greater than or equal to about 50 ms, greater than or equal to about60 ms, etc. Also, the LVAT threshold can be less than or equal to about25 ms, less than or equal to about 35 ms, less than or equal to about 45ms, less than or equal to about 55 ms, etc.

The method 446-2 can include determining that the paced setting causescomplete engagement of a Purkinje system in response to the RVAT, ASAT,and LVAT values being below their respective thresholds 777. As anexample, the RVAT value can be less than or equal to a threshold of 30ms, an ASAT value can be less than or equal to a threshold of 30 ms, andan LVAT value can be less than or equal to a threshold of 30 ms in orderto indicate that there is complete engagement of the Purkinje system.The Purkinje system can be partially and/or completely engaged throughthe His bundle, or bundle of His, which refers to a collection of heartmuscle cells specialized for electrical conduction. The His bundle cantransmit electrical impulses from the atrial-ventricular (AV) node(located between the atria and ventricles) to a point of the apex of thefascicular branches via the bundle branches. The fascicular branchesthen lead to the Purkinje fibers, which can provide fast electricalconduction to the ventricles, thereby causing the cardiac muscle of theventricles to contract more efficiently at a paced interval. Traditionalcardiac pacing therapies have included electrical stimulation ofventricular muscle which provides an alternative pathway of electricalactivation usually bypassing the fast conduction path provided by Hisbundle and Purkinje fibers, often resulting in slower cell to cellconduction and lower efficiency in cardiac contraction than thatpotentially achievable through successful stimulation of the His bundle.

In at least one example, the RVAT threshold can be less than, equal to,or greater than 20 ms, the ASAT threshold can be less than, equal to, orgreater than 20 ms, and the LVAT threshold can be less than, equal to,or greater than 20 ms. In other example, the RVAT threshold can be lessthan, equal to, or greater than 25 ms, the ASAT threshold can be lessthan, equal to, or greater than 25 ms, and the LVAT threshold can beless than, equal to, or greater than 25 ms. In other example, the RVATthreshold can be less than, equal to, or greater than 20 ms, the ASATthreshold can be less than, equal to, or greater than 20 ms, and theLVAT threshold can be less than, equal to, or greater than 30 ms. Inother example, the RVAT value can be less than, equal to, or greaterthan 30 ms, the ASAT threshold can be less than, equal to, or greaterthan 30 ms, and the LVAT threshold can be less than, equal to, orgreater than 20 ms. In another example, the RVAT threshold can be 30 ms,the ASAT threshold can be 20 ms, and the LVAT threshold can be 30 ms,and so forth for any combination of RVAT, ASAT, and LVAT thresholds.Thus, if during VfA pacing, the RVAT is less than or equal to an RVATthreshold, the ASAT is less than or equal to an ASAT threshold, and theLVAT is less than equal to an LVAT threshold, it may be determined thatthere is complete and/or substantially complete engagement of thePurkinje system.

The exemplary systems, methods, and graphical user interfaces describedherein may be used with respect to the implantation and configuration ofan implantable medical device (IMD) and/or one or more leads configuredto be located proximate one or more portions of a patient's heart, e.g.,proximate a location in the left ventricle). For example, the exemplarysystems, methods, and interfaces may be used in conjunction with anexemplary therapy system 10 described herein with reference to FIGS.8-12.

Although the present disclosure describes leadless and leadedimplantable medical devices, reference is first made to FIG. 8 showing aconceptual diagram of a cardiac therapy system 2 including anintracardiac medical device 10 that may be configured for single or dualchamber therapy and implanted in a patient's heart 8. In someembodiments, the device 10 may be configured for single chamber pacingand may, for example, switch between single chamber and multiple chamberpacing (e.g., dual or triple chamber pacing). As used herein,“intracardiac” refers to a device configured to be implanted entirelywithin a patient's heart, for example, to provide cardiac therapy. Thedevice 10 is shown implanted in the right atrium (RA) of the patient'sheart 8 in a target implant region 4. The device 10 may include one ormore fixation members 20 that anchor a distal end of the device againstthe atrial endocardium in a target implant region 4. The target implantregion 4 may lie between the Bundle of His 5 and the coronary sinus 3and may be adjacent the tricuspid valve 6. The device 10 may bedescribed as a ventricle-from-atrium (VfA) device, which may sense orprovide therapy to one or both ventricles (e.g., right ventricle, leftventricle, or both ventricles, depending on the circumstances) whilebeing generally disposed in the right atrium. In particular, the device10 may include a tissue-piercing electrode that may be implanted in thebasal and/or septal region of the left ventricular myocardium of thepatient's heart from the triangle of Koch region of the right atriumthrough the right atrial endocardium and central fibrous body.

The device 10 may be described as a leadless implantable medical device.As used herein, “leadless” refers to a device being free of a leadextending out of the patient's heart 8. In other words, a leadlessdevice may have a lead that does not extend from outside of thepatient's heart to inside of the patient's heart. Some leadless devicesmay be introduced through a vein, but once implanted, the device is freeof, or may not include, any transvenous lead and may be configured toprovide cardiac therapy without using any transvenous lead. A leadlessVfA device, in particular, does not use a lead to operably connect to anelectrode in the ventricle when a housing of the device is positioned inthe atrium. A leadless electrode may be coupled to the housing of themedical device without using a lead between the electrode and thehousing.

The device 10 may include one or more dart electrode 12 having astraight shaft extending from the distal end region of device 10,through the atrial myocardium and the central fibrous body, and into theventricular myocardium 14 or along the ventricular septum, withoutperforating entirely through the ventricular endocardial or epicardialsurfaces. The dart electrode 12 may carry an electrode at the distal endregion of the shaft for positioning the electrode within the ventricularmyocardium for sensing ventricular signals and delivering ventricularpulses (e.g., to depolarize the left ventricle to initiate a contractionof the left ventricle). In some examples, the electrode at the distalend region of the shaft is a cathode electrode provided for use in abipolar electrode pair for pacing and sensing. While the implant region4 is shown in FIG. 8 to enable one or more electrodes of the one or moredart electrodes 12 to be positioned in the ventricular myocardium, it isrecognized that a device having the aspects disclosed herein may beimplanted at other locations for multiple chamber pacing (e.g., dual ortriple chamber pacing), single chamber pacing with multiple chambersensing, single chamber pacing and/or sensing, or other clinical therapyand applications as appropriate.

The cardiac therapy system 2 may also include a separate medical device50 (depicted diagrammatically in FIG. 8), which may be positionedoutside the patient's heart 8 (e.g., subcutaneously) and may be operablycoupled to the patient's heart 8 to deliver cardiac therapy thereto. Inone example, separate medical device 50 may be an extravascular ICD. Insome embodiments, an extravascular ICD may include a defibrillation leadwith a defibrillation electrode. A therapy vector may exist between thedefibrillation electrode on the defibrillation lead and a housingelectrode of the ICD. Further, one or more electrodes of the ICD mayalso be used for sensing electrical signals related to the patient'sheart 8. The ICD may be configured to deliver shock therapy includingone or more defibrillation or cardioversion shocks. For example, if anarrhythmia is sensed, the ICD may send a pulse via the electrical leadwires to shock the heart and restore its normal rhythm. In someexamples, the ICD may deliver shock therapy without placing electricallead wires within the heart or attaching electrical wires directly tothe heart (subcutaneous ICDs). Examples of extravascular, subcutaneousICDs that may be used with the system 2 described herein may bedescribed in U.S. Pat. No. 9,278,229 (Reinke et al.), issued 8 Mar.2016, which is incorporated herein by reference in its entirety.

In the case of shock therapy, e.g., the defibrillation shocks providedby the defibrillation electrode of the defibrillation lead, separatemedical device 50 (e.g., extravascular ICD) may include a controlcircuit that uses a therapy delivery circuit to generate defibrillationshocks having any of a number of waveform properties, includingleading-edge voltage, tilt, delivered energy, pulse phases, and thelike. The therapy delivery circuit may, for instance, generatemonophasic, biphasic, or multiphasic waveforms. Additionally, thetherapy delivery circuit may generate defibrillation waveforms havingdifferent amounts of energy. For example, the therapy delivery circuitmay generate defibrillation waveforms that deliver a total of betweenapproximately 60-80 Joules (J) of energy for subcutaneousdefibrillation.

The separate medical device 50 may include a sensing circuit. Thesensing circuit may be configured to obtain electrical signals sensedvia one or more combinations of electrodes and process the obtainedsignals. The components of the sensing circuit may be analog components,digital components, or a combination thereof. The sensing circuit may,for example, include one or more sense amplifiers, filters, rectifiers,threshold detectors, analog-to-digital converters (ADCs) or the like.The sensing circuit may convert the sensed signals to digital form andprovide the digital signals to the control circuit for processing oranalysis. For example, the sensing circuit may amplify signals fromsensing electrodes and convert the amplified signals to multi-bitdigital signals by an ADC. The sensing circuit may also compareprocessed signals to a threshold to detect the existence of atrial orventricular depolarizations (e.g., P- or R-waves) and indicate theexistence of the atrial depolarization (e.g., P-waves) or ventriculardepolarizations (e.g., R-waves) to the control circuit.

The device 10 and the separate medical device 50 may cooperate toprovide cardiac therapy to the patient's heart 8. For example, thedevice 10 and the separate medical device 50 may be used to detecttachycardia, monitor tachycardia, and/or provide tachycardia-relatedtherapy. For example, the device 10 may communicate with the separatemedical device 50 wirelessly to trigger shock therapy using the separatemedical device 50. As used herein, “wirelessly” refers to an operativecoupling or connection without using a metal conductor between thedevice 10 and the separate medical device 50. In one example, wirelesscommunication may use a distinctive, signaling, or triggering electricalpulse provided by the device 10 that conducts through the patient'stissue and is detectable by the separate medical device 50. In anotherexample, wireless communication may use a communication interface (e.g.,an antenna) of the device 10 to provide electromagnetic radiation thatpropagates through patient's tissue and is detectable, for example,using a communication interface (e.g., an antenna) of the separatemedical device 50.

FIG. 9 is an enlarged conceptual diagram of the intracardiac medicaldevice 10 and anatomical structures of the patient's heart 8. Theintracardiac device 10 may include a housing 30. The housing 30 maydefine a hermetically sealed internal cavity in which internalcomponents of the device 10 reside, such as a sensing circuit, therapydelivery circuit, control circuit, memory, telemetry circuit, otheroptional sensors, and a power source as generally described inconjunction with FIG. 11 below. The housing 30 may be formed from anelectrically conductive material including titanium or titanium alloy,stainless steel, MP35N (a non-magnetic nickel-cobalt-chromium-molybdenumalloy), platinum alloy or other bio-compatible metal or metal alloy. Inother examples, the housing 30 may be formed from a non-conductivematerial including ceramic, glass, sapphire, silicone, polyurethane,epoxy, acetyl co-polymer plastics, polyether ether ketone (PEEK), aliquid crystal polymer, or other biocompatible polymer.

The housing 30 may be described as extending between a distal end region32 and a proximal end region 34 in a generally cylindrical shape tofacilitate catheter delivery. In other embodiments, the housing 30 maybe prismatic or any other shape so as to perform the functionality andutility described herein. The housing 30 may include a delivery toolinterface member 26, e.g., at the proximal end 34, for engaging with adelivery tool during implantation of the device 10.

All or a portion of the housing 30 may function as an electrode duringcardiac therapy, for example, in sensing and/or pacing. In the exampleshown, the housing-based electrode 24 is shown to circumscribe aproximal portion of the housing 30. When the housing 30 is formed froman electrically conductive material, such as a titanium alloy or otherexamples listed above, portions of the housing 30 may be electricallyinsulated by a non-conductive material, such as a coating of parylene,polyurethane, silicone, epoxy, or other biocompatible polymer, leavingone or more discrete areas of conductive material exposed to define theproximal housing-based electrode 24. When the housing 30 is formed froma non-conductive material, such as a ceramic, glass or polymer material,an electrically-conductive coating or layer, such as a titanium,platinum, stainless steel, or alloys thereof, may be applied to one ormore discrete areas of the housing 30 to form the proximal housing-basedelectrode 24. In other examples, the proximal housing-based electrode 24may be a component, such as a ring electrode, that is mounted orassembled onto the housing 30. The proximal housing-based electrode 24may be electrically coupled to internal circuitry of the device 10,e.g., via the electrically-conductive housing 30 or an electricalconductor when the housing 30 is a non-conductive material.

In the example shown, the proximal housing-based electrode 24 is locatednearer to the housing proximal end region 34 than the housing distal endregion 32 and is therefore referred to as a “proximal housing-basedelectrode” 24. In other examples, however, the housing-based electrode24 may be located at other positions along the housing 30, e.g.,relatively more distally than the position shown.

At the distal end region 32, the device 10 may include a distal fixationand electrode assembly 36, which may include one or more fixationmembers 20, in addition to one or more dart electrodes 12 of equal orunequal length. The dart electrode 12 may include a shaft 40 extendingdistally away from the housing distal end region 32 and may include oneor more electrode elements, such as a tip electrode 42 at or near thefree, distal end region of the shaft 40. The tip electrode 42 may have aconical or hemi-spherical distal tip with a relatively narrow tipdiameter (e.g., less than about 1 mm) for penetrating into and throughtissue layers without using a sharpened tip or needle-like tip havingsharpened or beveled edges.

The shaft 40 of the dart electrode 12 may be a normally straight memberand may be rigid. In other embodiments, the shaft 40 may be described asbeing relatively stiff but still possessing limited flexibility inlateral directions. Further, the shaft 40 may be non-rigid to allow somelateral flexing with heart motion. However, in a relaxed state, when notsubjected to any external forces, the shaft 40 may maintain a straightposition as shown to hold the tip electrode 42 spaced apart from thehousing distal end region 32 at least by the height 47 of the shaft 40.The dart electrode 12 may be configured to pierce through one or moretissue layers to position the tip electrode 42 within a desired tissuelayer, e.g., the ventricular myocardium. As such, the height 47 of theshaft 40 may correspond to the expected pacing site depth, and the shaftmay have a relatively high compressive strength along its longitudinalaxis to resist bending in a lateral or radial direction when pressedagainst the implant region 4. If a second dart electrode 12 is employed,its length may be unequal to the expected pacing site depth and may beconfigured to act as an indifferent electrode for delivering of pacingenergy to the tissue. A longitudinal axial force may be applied againstthe tip electrode 42, e.g., by applying longitudinal pushing force tothe proximal end 34 of the housing 30, to advance the dart electrode 12into the tissue within target implant region. The shaft 40 may belongitudinally non-compressive. The shaft 40 may be elasticallydeformable in lateral or radial directions when subjected to lateral orradial forces to allow temporary flexing, e.g., with tissue motion, butmay return to its normally straight position when lateral forcesdiminish. When the shaft 40 is not exposed to any external force, or toonly a force along its longitudinal central axis, the shaft 40 mayretain a straight, linear position as shown.

The one or more fixation members 20 may be described as one or more“tines” having a normally curved position. The tines may be held in adistally extended position within a delivery tool. The distal tips oftines may penetrate the heart tissue to a limited depth beforeelastically curving back proximally into the normally curved position(shown) upon release from the delivery tool. Further, the fixationmembers 20 may include one or more aspects described in, for example,U.S. Pat. No. 9,675,579 (Grubac et al.), issued 13 Jun. 2017, and U.S.Pat. No. 9,119,959 (Rys et al.), issued 1 Sep. 2015, each of which isincorporated herein by reference in its entirety.

In some examples, the distal fixation and electrode assembly 36 includesa distal housing-based electrode 22. In the case of using the device 10as a pacemaker for multiple chamber pacing (e.g., dual or triple chamberpacing) and sensing, the tip electrode 42 may be used as a cathodeelectrode paired with the proximal housing-based electrode 24 serving asa return anode electrode. Alternatively, the distal housing-basedelectrode 22 may serve as a return anode electrode paired with tipelectrode 42 for sensing ventricular signals and delivering ventricularpacing pulses. In other examples, the distal housing-based electrode 22may be a cathode electrode for sensing atrial signals and deliveringpacing pulses to the atrial myocardium in the target implant region 4.When the distal housing-based electrode 22 serves as an atrial cathodeelectrode, the proximal housing-based electrode 24 may serve as thereturn anode paired with the tip electrode 42 for ventricular pacing andsensing and as the return anode paired with the distal housing-basedelectrode 22 for atrial pacing and sensing.

As shown in this illustration, the target implant region 4 in somepacing applications is along the atrial endocardium 18, generallyinferior to the AV node 15 and the His bundle 5. The dart electrode 42may define the height 47 of the shaft 40 for penetrating through theatrial endocardium 18 in the target implant region 4, through thecentral fibrous body 16, and into the ventricular myocardium 14 withoutperforating through the ventricular endocardial surface 17. When theheight 47 of the dart electrode 12 is fully advanced into the targetimplant region 4, the tip electrode 42 may rest within the ventricularmyocardium 14, and the distal housing-based electrode 22 may bepositioned in intimate contact with or close proximity to the atrialendocardium 18. The dart electrode 12 may have a total combined height47 of tip electrode 42 and shaft 40 from about 3 mm to about 8 mm invarious examples. The diameter of the shaft 40 may be less than about 2mm, and may be about 1 mm or less, or even about 0.6 mm or less.

The device 10 may include a motion detector 11 within the housing 30.The motion detector 11 may be used to monitor mechanical activity, suchas atrial mechanical activity (e.g., an atrial contraction) and/orventricular mechanical activity (e.g., a ventricular contraction). Insome embodiments, the motion detector 11 may be used to detect rightatrial mechanical activity. A non-limiting example of a motion detector11 includes an accelerometer. In some embodiments, the mechanicalactivity detected by the motion detector 11 may be used to supplement orreplace electrical activity detected by one or more of the electrodes ofthe device 10. For example, the motion detector 11 may be used inaddition to, or as an alternative to, the proximal housing-basedelectrode 24.

The motion detector 11 may also be used for rate response detection orto provide a rate-responsive IMD. Various techniques related to rateresponse may be described in U.S. Pat. No. 5,154,170 (Bennett et al.),issued Oct. 13, 1992, entitled “Optimization for rate responsive cardiacpacemaker,” and U.S. Pat. No. 5,562,711 (Yerich et al.), issued Oct. 8,1996, entitled “Method and apparatus for rate-responsive cardiacpacing,” each of which is incorporated herein by reference in itsentirety.

FIG. 10 is a three-dimensional perspective view of the device 10 capableof cardiac therapy. As shown, the distal fixation and electrode assembly36 includes the distal housing-based electrode 22 implemented as a ringelectrode. The distal housing-based electrode 22 may be positioned inintimate contact with or operative proximity to atrial tissue whenfixation member tines 20 a, 20 b and 20 c of the fixation members 20,engage with the atrial tissue. The tines 20 a, 20 b and 20 c, which maybe elastically deformable, may be extended distally during delivery ofdevice 10 to the implant site. For example, the tines 20 a, 20 b, and 20c may pierce the atrial endocardial surface as the device 10 is advancedout of the delivery tool and flex back into their normally curvedposition (as shown) when no longer constrained within the delivery tool.As the tines 20 a, 20 b and 20 c curve back into their normal position,the fixation member 20 may pull the distal fixation member and electrodeassembly 36 toward the atrial endocardial surface. As the distalfixation member and electrode assembly 36 is pulled toward the atrialendocardium, the tip electrode 42 may be advanced through the atrialmyocardium and the central fibrous body and into the ventricularmyocardium. The distal housing-based electrode 22 may then be positionedagainst the atrial endocardial surface.

The distal housing-based electrode 22 may include a ring formed of anelectrically conductive material, such as titanium, platinum, iridium,or alloys thereof. The distal housing-based electrode 22 may be asingle, continuous ring electrode. In other examples, portions of thering may be coated with an electrically insulating coating, e.g.,parylene, polyurethane, silicone, epoxy, or other insulating coating, toreduce the electrically conductive surface area of the ring electrode.For instance, one or more sectors of the ring may be coated to separatetwo or more electrically conductive exposed surface areas of the distalhousing-based electrode 22. Reducing the electrically conductive surfacearea of the distal housing-based electrode 22, e.g., by coveringportions of the electrically conductive ring with an insulating coating,may increase the electrical impedance of the distal housing-based 22,and thereby, reduce the current delivered during a pacing pulse thatcaptures the myocardium, e.g., the atrial myocardial tissue. A lowercurrent drain may conserve the power source, e.g., one or morerechargeable or non-rechargeable batteries, of the device 10.

As described above, the distal housing-based electrode 22 may beconfigured as an atrial cathode electrode for delivering pacing pulsesto the atrial tissue at the implant site in combination with theproximal housing-based electrode 24 as the return anode. The electrodes22 and 24 may be used to sense atrial P-waves for use in controllingatrial pacing pulses (delivered in the absence of a sensed P-wave) andfor controlling atrial-synchronized ventricular pacing pulses deliveredusing the tip electrode 42 as a cathode and the proximal housing-basedelectrode 24 as the return anode. In other examples, the distalhousing-based electrode 22 may be used as a return anode in conjunctionwith the cathode tip electrode 42 for ventricular pacing and sensing.

FIG. 11 is a block diagram of circuitry that may be enclosed within thehousing 30 (FIG. 10) to provide the functions of cardiac therapy usingthe device 10 according to one example. The separate medical device 50(FIG. 8) may include some or all the same components, which may beconfigured in a similar manner. The electronic circuitry enclosed withinhousing 30 may include software, firmware, and hardware thatcooperatively monitor atrial and ventricular electrical cardiac signals,determine when a cardiac therapy is necessary, and/or deliver electricalpulses to the patient's heart according to programmed therapy mode andpulse control parameters. The electronic circuitry may include a controlcircuit 80 (e.g., including processing circuitry), a memory 82, atherapy delivery circuit 84, a sensing circuit 86, and/or a telemetrycircuit 88. In some examples, the device 10 includes one or more sensors90 for producing a signal that is correlated to a physiologicalfunction, state, or condition of the patient, such as a patient activitysensor, for use in determining a need for pacing therapy and/orcontrolling a pacing rate.

The power source 98 may provide power to the circuitry of the device 10including each of the components 80, 82, 84, 86, 88, and 90 as needed.The power source 98 may include one or more energy storage devices, suchas one or more rechargeable or non-rechargeable batteries. Theconnections between the power source 98 and each of the components 80,82, 84, 86, 88, and 90 are to be understood from the general blockdiagram illustrated but are not shown for the sake of clarity. Forexample, the power source 98 may be coupled to one or more chargingcircuits included in the therapy delivery circuit 84 for providing thepower needed to charge holding capacitors included in the therapydelivery circuit 84 that are discharged at appropriate times under thecontrol of the control circuit 80 for delivering pacing pulses, e.g.,according to a dual chamber pacing mode such as DDI(R). The power source98 may also be coupled to components of the sensing circuit 86, such assense amplifiers, analog-to-digital converters, switching circuitry,etc., sensors 90, the telemetry circuit 88, and the memory 82 to providepower to the various circuits.

The functional blocks shown represent functionality included in thedevice 10 and may include any discrete and/or integrated electroniccircuit components that implement analog, and/or digital circuitscapable of producing the functions attributed to the medical device 10herein. The various components may include processing circuitry, such asan application specific integrated circuit (ASIC), an electroniccircuit, a processor (shared, dedicated, or group), and memory thatexecute one or more software or firmware programs, a combinational logiccircuit, state machine, or other suitable components or combinations ofcomponents that provide the described functionality. The particular formof software, hardware, and/or firmware employed to implement thefunctionality disclosed herein will be determined primarily by theparticular system architecture employed in the medical device and by theparticular detection and therapy delivery methodologies employed by themedical device. Providing software, hardware, and/or firmware toaccomplish the described functionality in the context of any moderncardiac medical device system, given the disclosure herein, is withinthe abilities of one of skill in the art.

The memory 82 may include any volatile, non-volatile, magnetic, orelectrical non-transitory computer readable storage media, such asrandom-access memory (RAM), read-only memory (ROM), non-volatile RAM(NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory,or any other memory device. Furthermore, the memory 82 may include anon-transitory computer readable media storing instructions that, whenexecuted by one or more processing circuits, cause the control circuit80 and/or other processing circuitry to perform a single, dual, ortriple chamber pacing (e.g., single or multiple chamber pacing) functionor other sensing and therapy delivery functions attributed to the device10. The non-transitory computer-readable media storing the instructionsmay include any of the media listed above.

The control circuit 80 may communicate, e.g., via a data bus, with thetherapy delivery circuit 84 and the sensing circuit 86 for sensingcardiac electrical signals and controlling delivery of cardiacelectrical stimulation therapies in response to sensed cardiac events,e.g., P-waves and R-waves, or the absence thereof. The tip electrode 42,the distal housing-based electrode 22, and the proximal housing-basedelectrode 24 may be electrically coupled to the therapy delivery circuit84 for delivering electrical stimulation pulses to the patient's heartand to the sensing circuit 86 and for sensing cardiac electricalsignals.

The sensing circuit 86 may include an atrial (A) sensing channel 87 anda ventricular (V) sensing channel 89. The distal housing-based electrode22 and the proximal housing-based electrode 24 may be coupled to theatrial sensing channel 87 for sensing atrial signals, e.g., P-wavesattendant to the depolarization of the atrial myocardium. In examplesthat include two or more selectable distal housing-based electrodes, thesensing circuit 86 may include switching circuitry for selectivelycoupling one or more of the available distal housing-based electrodes tocardiac event detection circuitry included in the atrial sensing channel87. Switching circuitry may include a switch array, switch matrix,multiplexer, or any other type of switching device suitable toselectively couple components of the sensing circuit 86 to selectedelectrodes. The tip electrode 42 and the proximal housing-basedelectrode 24 may be coupled to the ventricular sensing channel 89 forsensing ventricular signals, e.g., R-waves attendant to thedepolarization of the ventricular myocardium.

Each of the atrial sensing channel 87 and the ventricular sensingchannel 89 may include cardiac event detection circuitry for detectingP-waves and R-waves, respectively, from the cardiac electrical signalsreceived by the respective sensing channels. The cardiac event detectioncircuitry included in each of the channels 87 and 89 may be configuredto amplify, filter, digitize, and rectify the cardiac electrical signalreceived from the selected electrodes to improve the signal quality fordetecting cardiac electrical events. The cardiac event detectioncircuitry within each channel 87 and 89 may include one or more senseamplifiers, filters, rectifiers, threshold detectors, comparators,analog-to-digital converters (ADCs), timers, or other analog or digitalcomponents. A cardiac event sensing threshold, e.g., a P-wave sensingthreshold and an R-wave sensing threshold, may be automatically adjustedby each respective sensing channel 87 and 89 under the control of thecontrol circuit 80, e.g., based on timing intervals and sensingthreshold values determined by the control circuit 80, stored in thememory 82, and/or controlled by hardware, firmware, and/or software ofthe control circuit 80 and/or the sensing circuit 86.

Upon detecting a cardiac electrical event based on a sensing thresholdcrossing, the sensing circuit 86 may produce a sensed event signal thatis passed to the control circuit 80. For example, the atrial sensingchannel 87 may produce a P-wave sensed event signal in response to aP-wave sensing threshold crossing. The ventricular sensing channel 89may produce an R-wave sensed event signal in response to an R-wavesensing threshold crossing. The sensed event signals may be used by thecontrol circuit 80 for setting pacing escape interval timers thatcontrol the basic time intervals used for scheduling cardiac pacingpulses. A sensed event signal may trigger or inhibit a pacing pulsedepending on the particular programmed pacing mode. For example, aP-wave sensed event signal received from the atrial sensing channel 87may cause the control circuit 80 to inhibit a scheduled atrial pacingpulse and schedule a ventricular pacing pulse at a programmedatrioventricular (AV) pacing interval. If an R-wave is sensed before theAV pacing interval expires, the ventricular pacing pulse may beinhibited. If the AV pacing interval expires before the control circuit80 receives an R-wave sensed event signal from the ventricular sensingchannel 89, the control circuit 80 may use the therapy delivery circuit84 to deliver the scheduled ventricular pacing pulse synchronized to thesensed P-wave.

In some examples, the device 10 may be configured to deliver a varietyof pacing therapies including bradycardia pacing, cardiacresynchronization therapy, post-shock pacing, and/or tachycardia-relatedtherapy, such as ATP, among others. For example, the device 10 may beconfigured to detect non-sinus tachycardia and deliver ATP. The controlcircuit 80 may determine cardiac event time intervals, e.g., PPintervals between consecutive P-wave sensed event signals received fromthe atrial sensing channel 87, RR intervals between consecutive R-wavesensed event signals received from the ventricular sensing channel 89,and P-R and/or R-P intervals received between P-wave sensed eventsignals and R-wave sensed event signals. These intervals may be comparedto tachycardia detection intervals for detecting non-sinus tachycardia.Tachycardia may be detected in a given heart chamber based on athreshold number of tachycardia detection intervals being detected.

The therapy delivery circuit 84 may include atrial pacing circuit 83 andventricular pacing circuit 85. Each pacing circuit 83 and 85 may includecharging circuitry, one or more charge storage devices such as one ormore low voltage holding capacitors, an output capacitor, and/orswitching circuitry that controls when the holding capacitor(s) arecharged and discharged across the output capacitor to deliver a pacingpulse to the pacing electrode vector coupled to respective pacingcircuits 83 or 85. The tip electrode 42 and the proximal housing-basedelectrode 24 may be coupled to the ventricular pacing circuit 85 as abipolar cathode and anode pair for delivering ventricular pacing pulses,e.g., upon expiration of an AV or VV pacing interval set by the controlcircuit 80 for providing atrial-synchronized ventricular pacing and abasic lower ventricular pacing rate.

The atrial pacing circuit 83 may be coupled to the distal housing-basedelectrode 22 and the proximal housing-based electrode 24 to deliveratrial pacing pulses. The control circuit 80 may set atrial pacingintervals according to a programmed lower pacing rate or a temporarylower rate set according to a rate-responsive sensor indicated pacingrate. Atrial pacing circuit may be controlled to deliver an atrialpacing pulse if the atrial pacing interval expires before a P-wavesensed event signal is received from the atrial sensing channel 87. Thecontrol circuit 80 starts an AV pacing interval in response to adelivered atrial pacing pulse to provide synchronized multiple chamberpacing (e.g., dual or triple chamber pacing).

Charging of a holding capacitor of the atrial or ventricular pacingcircuit 83 or 85 to a programmed pacing voltage amplitude anddischarging of the capacitor for a programmed pacing pulse width may beperformed by the therapy delivery circuit 84 according to controlsignals received from the control circuit 80. For example, a pace timingcircuit included in the control circuit 80 may include programmabledigital counters set by a microprocessor of the control circuit 80 forcontrolling the basic pacing time intervals associated with varioussingle chamber or multiple chamber pacing (e.g., dual or triple chamberpacing) modes or anti-tachycardia pacing sequences. The microprocessorof the control circuit 80 may also set the amplitude, pulse width,polarity, or other characteristics of the cardiac pacing pulses, whichmay be based on programmed values stored in the memory 82.

The device 10 may include other sensors 90 for sensing signals from thepatient for use in determining a need for and/or controlling electricalstimulation therapies delivered by the therapy delivery circuit 84. Insome examples, a sensor indicative of a need for increased cardiacoutput may include a patient activity sensor, such as an accelerometer.An increase in the metabolic demand of the patient due to increasedactivity as indicated by the patient activity sensor may be determinedby the control circuit 80 for use in determining a sensor-indicatedpacing rate.

Control parameters utilized by the control circuit 80 for sensingcardiac events and controlling pacing therapy delivery may be programmedinto the memory 82 via the telemetry circuit 88, which may also bedescribed as a communication interface. The telemetry circuit 88includes a transceiver and antenna for communicating with an externaldevice such as a programmer or home monitor, using radio frequencycommunication or other communication protocols. The control circuit 80may use the telemetry circuit 88 to receive downlink telemetry from andsend uplink telemetry to the external device. In some cases, thetelemetry circuit 88 may be used to transmit and receive communicationsignals to/from another medical device implanted in the patient.

FIG. 12 is a three-dimensional perspective view of another leadlessintracardiac medical device 710 that may be configured for single ormultiple chamber cardiac therapy (e.g., dual or triple chamber cardiactherapy) according to another example. The device 710 may include ahousing 730 having an outer sidewall 735, shown as a cylindrical outersidewall, extending from a housing distal end region 732 to a housingproximal end region 734. The housing 730 may enclose electroniccircuitry configured to perform single or multiple chamber cardiactherapy, including atrial and ventricular cardiac electrical signalsensing and pacing the atrial and ventricular chambers. Delivery toolinterface member 726 is shown on the housing proximal end region 734.

A distal fixation and electrode assembly 736 may be coupled to thehousing distal end region 732. The distal fixation and electrodeassembly 736 may include an electrically insulative distal member 772coupled to the housing distal end region 732. The tissue piercingelectrode 712 extends away from the housing distal end region 732, andmultiple non-tissue piercing electrodes 722 may be coupled directly tothe insulative distal member 772. The tissue piercing electrode 712extends in a longitudinal direction away from the housing distal endregion 732 and may be coaxial with the longitudinal center axis 731 ofthe housing 730.

The tissue piercing distal electrode 712 may include an electricallyinsulated shaft 740 and a tip electrode 742. In some examples, thetissue piercing distal electrode 712 is an active fixation memberincluding a helical shaft 740 and a distal cathode tip electrode 742.The helical shaft 740 may extend from a shaft distal end region 743 to ashaft proximal end region 741, which may be directly coupled to theinsulative distal member 772. The helical shaft 740 may be coated withan electrically insulating material, e.g., parylene or other exampleslisted herein, to avoid sensing or stimulation of cardiac tissue alongthe shaft length. The tip electrode 742 is at the shaft distal endregion 743 and may serve as a cathode electrode for deliveringventricular pacing pulses and sensing ventricular electrical signalsusing the proximal housing-based electrode 724 as a return anode whenthe tip electrode 742 is advanced into ventricular tissue. The proximalhousing-based electrode 724 may be a ring electrode circumscribing thehousing 730 and may be defined by an uninsulated portion of thelongitudinal sidewall 735. Other portions of the housing 730 not servingas an electrode may be coated with an electrically insulating materialas described above in conjunction with FIG. 9.

Using two or more tissue-piercing electrodes (e.g., of any type)penetrating into the LV myocardium may be used for more localized pacingcapture and may mitigate ventricular pacing spikes affecting capturingatrial tissue. In some embodiments, multiple tissue-piercing electrodesmay include two or more of a dart-type electrode (e.g., electrode 12 ofFIGS. 8-9), a helical-type electrode (e.g., electrode 712) Non-limitingexamples of multiple tissue-piercing electrodes include two dartelectrodes, a helix electrode with a dart electrode extendingtherethrough (e.g., through the center), or dual intertwined helixes.Multiple tissue-piercing electrodes may also be used for bipolar ormulti-polar pacing.

In some embodiments, one or more tissue-piercing electrodes (e.g., ofany type) that penetrate into the LV myocardium may be a multi-polartissue-piercing electrode. A multi-polar tissue-piercing electrode mayinclude one or more electrically active and electrically separateelements, which may enable bipolar or multi-polar pacing from one ormore tissue-piercing electrodes.

Multiple non-tissue piercing electrodes 722 may be provided along aperiphery of the insulative distal member 772, peripheral to the tissuepiercing electrode 712. The insulative distal member 772 may define adistal-facing surface 738 of the device 710 and a circumferentialsurface 739 that circumscribes the device 710 adjacent to the housinglongitudinal sidewall 735. Non-tissue piercing electrodes 722 may beformed of an electrically conductive material, such as titanium,platinum, iridium, or alloys thereof. In the illustrated embodiment, sixnon-tissue piercing electrodes 722 are spaced apart radially at equaldistances along the outer periphery of insulative distal member 772,however, two or more non-tissue piercing electrodes 722 may be provided.

Non-tissue piercing electrodes 722 may be discrete components eachretained within a respective recess 774 in the insulative member 772sized and shaped to mate with the non-tissue piercing electrode 722. Inother examples, the non-tissue piercing electrodes 722 may each be anuninsulated, exposed portion of a unitary member mounted within or onthe insulative distal member 772. Intervening portions of the unitarymember not functioning as an electrode may be insulated by theinsulative distal member 772 or, if exposed to the surroundingenvironment, may be coated with an electrically insulating coating,e.g., parylene, polyurethane, silicone, epoxy, or other insulatingcoating.

When the tissue piercing electrode 712 is advanced into cardiac tissue,at least one non-tissue piercing electrode 722 may be positionedagainst, in intimate contact with, or in operative proximity to, acardiac tissue surface for delivering pulses and/or sensing cardiacelectrical signals produced by the patient's heart. For example,non-tissue piercing electrodes 722 may be positioned in contact withright atrial endocardial tissue for pacing and sensing in the atriumwhen the tissue piercing electrode 712 is advanced into the atrialtissue and through the central fibrous body until the distal tipelectrode 742 is positioned in direct contact with ventricular tissue,e.g., ventricular myocardium and/or a portion of the ventricularconduction system.

Non-tissue piercing electrodes 722 may be coupled to the therapydelivery circuit 84 and the sensing circuit 86 (see FIG. 11) enclosed bythe housing 730 to function collectively as a cathode electrode fordelivering atrial pacing pulses and for sensing atrial electricalsignals, e.g., P-waves, in combination with the proximal housing-basedelectrode 724 as a return anode. Switching circuitry included in thesensing circuit 86 may be activated under the control of the controlcircuit 80 to couple one or more of the non-tissue piercing electrodesto the atrial sensing channel 87. Distal, non-tissue piercing electrodes722 may be electrically isolated from each other so that each individualone of the electrodes 722 may be individually selected by switchingcircuitry included in the therapy delivery circuit 84 to serve alone orin a combination of two or more of the electrodes 722 as an atrialcathode electrode. Switching circuitry included in the therapy deliverycircuit 84 may be activated under the control of the control circuit 80to couple one or more of the non-tissue piercing electrodes 722 to theatrial pacing circuit 83. Two or more of the non-tissue piercingelectrodes 722 may be selected at a time to operate as a multi-pointatrial cathode electrode.

Certain non-tissue piercing electrodes 722 selected for atrial pacingand/or atrial sensing may be selected based on atrial capture thresholdtests, electrode impedance, P-wave signal strength in the cardiacelectrical signal, or other factors. For example, a single one or anycombination of two or more individual non-tissue piercing electrodes 722functioning as a cathode electrode that provides an optimal combinationof a low pacing capture threshold amplitude and relatively highelectrode impedance may be selected to achieve reliable atrial pacingusing minimal current drain from the power source 98.

In some instances, the distal-facing surface 738 may uniformly contactthe atrial endocardial surface when the tissue piercing electrode 712anchors the housing 730 at the implant site. In that case, all theelectrodes 722 may be selected together to form the atrial cathode.Alternatively, every other one of the electrodes 722 may be selectedtogether to form a multi-point atrial cathode having a higher electricalimpedance that is still uniformly distributed along the distal-facingsurface 738. Alternatively, a subset of one or more electrodes 722 alongone side of the insulative distal member 772 may be selected to providepacing at a desired site that achieves the lowest pacing capturethreshold due to the relative location of the electrodes 722 to theatrial tissue being paced.

In other instances, the distal-facing surface 738 may be oriented at anangle relative to the adjacent endocardial surface depending on thepositioning and orientation at which the tissue piercing electrode 712enters the cardiac tissue. In this situation, one or more of thenon-tissue piercing electrodes 722 may be positioned in closer contactwith the adjacent endocardial tissue than other non-tissue piercingelectrodes 722, which may be angled away from the endocardial surface.By providing multiple non-tissue piercing electrodes along the peripheryof the insulative distal member 772, the angle of the tissue piercingelectrode 712 and the housing distal end region 732 relative to thecardiac surface, e.g., the right atrial endocardial surface, may not berequired to be substantially parallel. Anatomical and positionaldifferences may cause the distal-facing surface 738 to be angled oroblique to the endocardial surface, however, multiple non-tissuepiercing electrodes 722 distributed along the periphery of theinsulative distal member 772 increase the likelihood of good contactbetween one or more electrodes 722 and the adjacent cardiac tissue topromote acceptable pacing thresholds and reliable cardiac event sensingusing at least a subset of multiple electrodes 722. Contact or fixationcircumferentially along the entire periphery of the insulative distalmember 772 may not be required.

The non-tissue piercing electrodes 722 are shown to each include a firstportion 722 a extending along the distal-facing surface 738 and a secondportion 722 b extending along the circumferential surface 739. The firstportion 722 a and the second portion 722 b may be continuous exposedsurfaces such that the active electrode surface wraps around aperipheral edge 776 of the insulative distal member 772 that joins thedistal facing surface 738 and the circumferential surface 739. Thenon-tissue piercing electrodes 722 may include one or more of theelectrodes 772 along the distal-facing surface 738, one or moreelectrodes along the circumferential surface 739, one or more electrodeseach extending along both of the distal-facing surface 738 and thecircumferential surface 739, or any combination thereof. The exposedsurface of each of the non-tissue piercing electrodes 722 may be flushwith respective distal-facing surfaces 738 and/or circumferentialsurfaces. In other examples, each of the non-tissue piercing electrodes722 may have a raised surface that protrudes from the insulative distalmember 772. Any raised surface of the electrodes 722, however, maydefine a smooth or rounded, non-tissue piercing surface.

The distal fixation and electrode assembly 736 may seal the distal endregion of the housing 730 and may provide a foundation on which theelectrodes 722 are mounted. The electrodes 722 may be referred to ashousing-based electrodes. The electrodes 722 may not be not carried by ashaft or other extension that extends the active electrode portion awayfrom the housing 730, like the distal tip electrode 742 residing at thedistal tip of the helical shaft 740 extending away from the housing 730.Other examples of non-tissue piercing electrodes presented herein thatare coupled to a distal-facing surface and/or a circumferential surfaceof an insulative distal member include the distal housing-based ringelectrode 22 (FIG. 10), the distal housing-based ring electrodeextending circumferentially around the assembly 36 (FIG. 10), buttonelectrodes, other housing-based electrodes, and other circumferentialring electrodes. Any non-tissue piercing electrodes directly coupled toa distal insulative member, peripherally to a central tissue-piercingelectrode, may be provided to function individually, collectively, or inany combination as a cathode electrode for delivering pacing pulses toadjacent cardiac tissue. When a ring electrode, such as the distal ringelectrode 22 and/or a circumferential ring electrode, is provided,portions of the ring electrode may be electrically insulated by acoating to provide multiple distributed non-tissue piercing electrodesalong the distal-facing surface and/or the circumferential surface ofthe insulative distal member.

The non-tissue piercing electrodes 722 and other examples listed aboveare expected to provide more reliable and effective atrial pacing andsensing than a tissue piercing electrode provided along the distalfixation and electrode assembly 736. The atrial chamber walls arerelatively thin compared to ventricular chamber walls. A tissue piercingatrial cathode electrode may extend too deep within the atrial tissueleading to inadvertent sustained or intermittent capture of ventriculartissue. A tissue piercing atrial cathode electrode may lead tointerference with sensing atrial signals due to ventricular signalshaving a larger signal strength in the cardiac electrical signalreceived via tissue-piercing atrial cathode electrodes that are incloser physical proximity to the ventricular tissue. The tissue piercingelectrode 712 may be securely anchored into ventricular tissue forstabilizing the implant position of the device 710 and providingreasonable certainty that the tip electrode 742 is sensing and pacing inventricular tissue while the non-tissue piercing electrodes 722 arereliably pacing and sensing in the atrium. When the device 710 isimplanted in the target implant region 4, e.g., as shown in FIG. 8 theventricular septum, the tip electrode 742 may reach left ventriculartissue for pacing of the left ventricle while the non-tissue piercingelectrodes 722 provide pacing and sensing in the right atrium. Thetissue piercing electrode 712 may be in the range of about 4 to about 8mm in length from the distal-facing surface 738 to reach leftventricular tissue. In some instances, the device 710 may achievefour-chamber pacing by delivering atrial pacing pulses from the atrialpacing circuit 83 via the non-tissue piercing electrodes 722 in thetarget implant region 4 to achieve bi-atrial (right and left atrial)capture and by delivering ventricular pacing pulses from the ventricularpacing circuit 85 via the tip electrode 742 advanced into ventriculartissue from the target implant region 4 to achieve biventricular (rightand left ventricular) capture.

FIG. 13 is a two-dimensional (2D) ventricular map 300 of a patient'sheart (e.g., a top-down view) showing the left ventricle 320 in astandard 17 segment view and the right ventricle 322. The map 300includes a plurality of areas 326 corresponding to different regions ofa human heart. As illustrated, the areas 326 are numerically labeled1-17 (which, e.g., correspond to a standard 17 segment model of a humanheart, correspond to 17 segments of the left ventricle of a human heart,etc.). Areas 326 of the map 300 may include basal anterior area 1, basalanteroseptal area 2, basal inferoseptal area 3, basal inferior area 4,basal inferolateral area 5, basal anterolateral area 6, mid-anteriorarea 7, mid-anteroseptal area 8, mid-inferoseptal area 9, mid-inferiorarea 10, mid-inferolateral area 11, mid-anterolateral area 12, apicalanterior area 13, apical septal area 14, apical inferior area 15, apicallateral area 16, and apex area 17. The inferoseptal and anteroseptalareas of the right ventricle 322 are also illustrated, as well as theright bunch branch (RBB) and left bundle branch (LBB).

In some embodiments, any of the tissue-piercing electrodes of thepresent disclosure may be implanted through the right atrialendocardium. In particular, the tissue-piercing electrode may beimplanted from the triangle of Koch region of the right atrium.

Once implanted, the tissue-piercing electrode may be positioned in thetarget implant region 4 (FIG. 8), such as the basal and/or septal regionof the left ventricular myocardium. With reference to map 300, the basalregion includes one or more of the basal anterior area 1, basalanteroseptal area 2, basal inferoseptal area 3, basal inferior area 4,mid-anterior area 7, mid-anteroseptal area 8, mid-inferoseptal area 9,and mid-inferior area 10. With reference to map 300, the septal regionincludes one or more of the basal anteroseptal area 2, basalanteroseptal area 3, mid-anteroseptal area 8, mid-inferoseptal area 9,and apical septal area 14.

In some embodiments, the tissue-piercing electrode may be positioned inthe basal and/or septal area of the left ventricular myocardium whenimplanted. The basal and/or septal region may include one or more of thebasal anteroseptal area 2, basal inferoseptal area 3, mid-anteroseptalarea 8, and mid-inferoseptal area 9.

In some embodiments, the tissue-piercing electrode may be positioned inthe basal and/or septal region of the left ventricular myocardium whenimplanted. The high inferior/posterior basal and/or septal region of theleft ventricular myocardium may include a portion of at least one of thebasal inferoseptal area 3 and mid-inferoseptal area 9. For example, thehigh inferior/posterior basal and/or septal region may include region324 illustrated generally as a dashed-line boundary. As shown, thedashed line boundary represents an approximation of about where the highinferior/posterior basal and/or septal region and may take somewhatdifferent shape or size depending on the particular application.

The techniques described in this disclosure, including those attributedto the IMD 16, the computing apparatus 140, and/or various constituentcomponents, may be implemented, at least in part, in hardware, software,firmware, or any combination thereof. For example, various aspects ofthe techniques may be implemented within one or more processors,including one or more microprocessors, DSPs, ASICs, FPGAs, or any otherequivalent integrated or discrete logic circuitry, as well as anycombinations of such components, embodied in programmers, such asphysician or patient programmers, stimulators, image processing devices,or other devices. The term “module,” “processor,” or “processingcircuitry” may generally refer to any of the foregoing logic circuitry,alone or in combination with other logic circuitry, or any otherequivalent circuitry.

Such hardware, software, and/or firmware may be implemented within thesame device or within separate devices to support the various operationsand functions described in this disclosure. In addition, any of thedescribed units, modules, or components may be implemented together orseparately as discrete but interoperable logic devices. Depiction ofdifferent features as modules or units is intended to highlightdifferent functional aspects and does not necessarily imply that suchmodules or units must be realized by separate hardware or softwarecomponents. Rather, functionality associated with one or more modules orunits may be performed by separate hardware or software components, orintegrated within common or separate hardware or software components.

When implemented in software, the functionality ascribed to the systems,devices and techniques described in this disclosure may be embodied asinstructions on a computer-readable medium such as RAM, ROM, NVRAM,EEPROM, FLASH memory, magnetic data storage media, optical data storagemedia, or the like. The instructions may be executed by one or moreprocessors to support one or more aspects of the functionality describedin this disclosure.

This disclosure has been provided with reference to illustrativeembodiments and is not meant to be construed in a limiting sense. Asdescribed previously, one skilled in the art will recognize that othervarious illustrative applications may use the techniques as describedherein to take advantage of the beneficial characteristics of theapparatus and methods described herein. Various modifications of theillustrative embodiments, as well as additional embodiments of thedisclosure, will be apparent upon reference to this description.

ILLUSTRATIVE EMBODIMENTS Embodiment 1

A system comprising:

electrode apparatus comprising a plurality of external electrodes tomonitor electrical activity from tissue of a patient; and

computing apparatus comprising processing circuitry and coupled to theelectrode apparatus and configured to:

-   -   monitor electrical activity using the plurality of external        electrodes;    -   generate paced electrical heterogeneity information (EHI) based        on the monitored electrical activity during delivery of        ventricle from atrium (VfA) pacing therapy at one or more VfA        paced settings, wherein the paced EHI is representative of at        least one of mechanical cardiac functionality and electrical        cardiac functionality; and    -   determine whether the one or more VfA paced settings for the VfA        pacing therapy are acceptable based on the paced EHI.

Embodiment 2

The system of embodiment 1, wherein the one or more VfA paced settingscomprise at least one of a voltage, a pulse width, timing of a V-pacingrelative to intrinsic or paced atrial timing, and pacing rate.

Embodiment 3

The system of any one of embodiments 1 to 2, wherein the one or more VfApaced settings comprises a location of at least one implantableelectrode wherein the location comprises at least one of depth andangle.

Embodiment 4

The system of any one of embodiments 1 to 3, wherein the one or more VfApaced settings comprises at least one of a pacing polarity, a pacingvector, and a number of pacing electrodes used.

Embodiment 5

The system of any one of embodiments 1 to 4, wherein the system furthercomprises a VfA pacing therapy apparatus, wherein the VfA pacing therapyapparatus comprises a tissue-piercing electrode implantable from thetriangle of Koch region of the right atrium through the right atrialendocardium and central fibrous body to deliver the VfA pacing therapyto the left ventricle in the basal and/or septal region of the leftventricular myocardium of the patient's heart.

Embodiment 6

The system of any one of embodiments 1 to 5, wherein the VfA pacedsettings comprises a location of the at least one implantable electrodeproximate the high posterior basal and/or septal area of the leftventricle of the patient.

Embodiment 7

The system of any one of embodiments 1 to 6, wherein the plurality ofexternal electrodes comprises surface electrodes positioned in an arrayconfigured to be located proximate skin of a torso of the patient.

Embodiment 8

The system of any one of embodiments 1 to 7, wherein the paced EHIcomprises a metric of electrical heterogeneity,

wherein the determining whether the one or more VfA paced settings forthe VfA pacing therapy are acceptable comprises determining that the oneor more VfA paced settings are acceptable if the metric of electricalheterogeneity is less than or equal to a threshold.

Embodiment 9

The system of any one of embodiments 1 to 8, wherein the determiningwhether the one or more VfA paced settings for the VfA pacing therapyare acceptable comprises:

generating baseline EHI from the monitored electrical activity withoutdelivery of the VfA pacing therapy;

comparing the baseline EHI to the paced EHI; and

determining that the one or more VfA paced settings are acceptable basedon the comparison of the baseline EHI to the paced EHI.

Embodiment 10

The system of any one of embodiments 1 to 9, wherein the electricalheterogeneity information comprises at least one metric of electricalheterogeneity, wherein the at least one metric of electricalheterogeneity comprises anterior-septal activation times (ASAT), whereinASAT comprises activation times monitored from external electrodes ofthe plurality of external electrodes that correspond to theanterior-septal region of the heart of the patient.

Embodiment 11

The system of any one of embodiments 1 to 10, wherein the electricalheterogeneity information comprises at least one metric of electricalheterogeneity, wherein the at least one metric of electricalheterogeneity comprises at least one of anterior-septal activation times(ASAT), a standard deviation of activation times (SDAT), a compositeleft ventricular activation time (LVAT), and a composite rightventricular activation time (RVAT).

Embodiment 12

The system of any one of embodiments 1 to 11, wherein the computingapparatus is further configured to adjust the one or more VfA pacedsettings for the VfA pacing therapy based on whether the VfA pacingtherapy is acceptable; and

wherein the adjusted one or more VfA paced settings is determined to beacceptable in response to the VfA pacing therapy correcting a bundlebranch block (BBB).

Embodiment 13

The system of any one of embodiments 1 to 12, wherein the computingapparatus is further configured to adjust the one or more VfA pacedsettings for the VfA pacing therapy based on whether the VfA pacingtherapy is acceptable; and

wherein the adjusted one or more VfA paced settings is determined to beacceptable in response to the VfA pacing therapy completely engaging aPurkinje system of the heart of the patient.

Embodiment 14

A method comprising:

monitoring electrical activity from tissue of a patient using aplurality of external electrodes;

generating paced electrical heterogeneity information (EHI) based on themonitored electrical activity during delivery of ventricle from atrium(VfA) pacing therapy at one or more VfA paced settings, wherein thepaced EHI is representative of at least one of mechanical cardiacfunctionality and electrical cardiac functionality; and

determining whether the one or more VfA paced settings for the VfApacing therapy are acceptable based on the paced EHI.

Embodiment 15

The method of embodiment 14, wherein the one or more VfA paced settingscomprise at least one of a voltage, a pulse width, timing of a V-pacingrelative to intrinsic or paced atrial timing, and pacing rate.

Embodiment 16

The method of any one of embodiments 14 to 15, wherein the one or moreVfA paced settings comprises a location of at least one implantableelectrode wherein the location comprises at least one of depth andangle.

Embodiment 17

The method of any one of embodiments 14 to 16, wherein the one or moreVfA paced settings comprises at least one of a pacing polarity, a pacingvector, and a number of pacing electrodes used.

Embodiment 18

The method of any one of embodiments 14 to 17, wherein the delivery ofthe VfA pacing therapy is performed by a VfA therapy apparatus, whereinthe VfA pacing therapy apparatus comprises a tissue-piercing electrodeimplantable from the triangle of Koch region of the right atrium throughthe right atrial endocardium and central fibrous body to deliver the VfApacing therapy to the left ventricle in the basal and/or septal regionof the left ventricular myocardium of the patient.

Embodiment 19

The method of embodiment 18, wherein the VfA paced settings comprises alocation of the at least one implantable electrode proximate the highposterior basal and/or septal area of the left ventricle of the patient.

Embodiment 20

The method of any one of embodiments 14 to 19, wherein the plurality ofexternal electrodes comprises surface electrodes positioned in an arrayconfigured to be located proximate skin of a torso of the patient.

Embodiment 21

The method of any one of embodiments 14 to 20, wherein the paced EHIcomprises a metric of electrical heterogeneity, wherein the determiningwhether the one or more VfA paced settings for the VfA pacing therapyare acceptable comprises determining that the one or more VfA pacedsettings are acceptable if the metric of electrical heterogeneity isless than or equal to a threshold.

Embodiment 22

The method of any one of embodiments 14 to 21, wherein the determiningwhether the one or more VfA paced settings for the VfA pacing therapyare acceptable comprises:

generating baseline EHI from the monitored electrical activity withoutdelivery of the VfA pacing therapy;

comparing the baseline EHI to the paced EHI; and

determining that the one or more VfA paced settings are acceptable basedon the comparison of the baseline EHI to the paced EHI.

Embodiment 23

The method of any one of embodiments 14 to 22, wherein the electricalheterogeneity information comprises at least one metric of electricalheterogeneity, wherein the at least one metric of electricalheterogeneity comprises anterior-septal activation times (ASAT), whereinASAT comprises activation times monitored from external electrodes ofthe plurality of external electrodes that correspond to theanterior-septal region of the heart of the patient.

Embodiment 24

The method of any one of embodiments 14 to 23, wherein the electricalheterogeneity information comprises at least one metric of electricalheterogeneity, wherein the at least one metric of electricalheterogeneity comprises at least one of anterior-septal activation times(ASAT), a standard deviation of activation times (SDAT), a compositeleft ventricular activation time (LVAT), and a composite rightventricular activation time (RVAT).

Embodiment 25

The method of any one of embodiments 14 to 24, further comprisingadjusting the one or more VfA paced settings for the VfA pacing therapybased on whether the VfA pacing therapy is acceptable; and

wherein the adjusted one or more VfA paced settings is determined to beacceptable in response to the VfA pacing therapy correcting a bundlebranch block (BBB).

Embodiment 26

The method of any one of embodiments 14 to 26, wherein the computingapparatus is further configured to adjust the one or more VfA pacedsettings for the VfA pacing therapy based on whether the VfA pacingtherapy is acceptable; and

wherein the adjusted one or more VfA paced settings is determined to beacceptable in response to the VfA pacing therapy completely engaging aPurkinje system of the heart of the patient.

Embodiment 27

A system comprising:

electrode apparatus comprising a plurality of external electrodes tomonitor electrical activity from tissue of a patient; and

computing apparatus comprising processing circuitry and coupled to theelectrode apparatus and configured to:

-   -   monitor electrical activity using the plurality of external        electrodes during delivery of ventricle from atrium (VfA) pacing        therapy;    -   generate electrical heterogeneity information (EHI) during        delivery of VfA pacing therapy;    -   determine whether a VfA paced setting for the VfA pacing therapy        is acceptable based on the EHI generated from the electrical        activity using the VfA paced setting; and    -   adjust the paced setting for the VfA pacing therapy based on        whether the VfA pacing therapy is acceptable.

What is claimed:
 1. A system comprising: electrode apparatus comprisinga plurality of external electrodes to monitor electrical activity fromtissue of a patient and computing apparatus comprising processingcircuitry and coupled to the electrode apparatus and configured to:monitor electrical activity using the plurality of external electrodes;generate paced electrical heterogeneity information (EHI) based on themonitored electrical activity during delivery of ventricle from atrium(VfA) pacing therapy at one or more VfA paced settings, wherein thepaced EHI is representative of at least one of mechanical cardiacfunctionality and electrical cardiac functionality; and determinewhether the one or more VfA paced settings for the VfA pacing therapyare acceptable based on the paced EHI.
 2. The system of claim 1, whereinthe one or more VfA paced settings comprise at least one of a voltage, apulse width, timing of a V-pacing relative to intrinsic or paced atrialtiming, and pacing rate.
 3. The system of claim 1, wherein the one ormore VfA paced settings comprises a location of at least one implantableelectrode wherein the location comprises at least one of depth andangle.
 4. The system of claim 1, wherein the one or more VfA pacedsettings comprises at least one of a pacing polarity, a pacing vector,and a number of pacing electrodes used.
 5. The system of claim 1,wherein the system further comprises a VfA pacing therapy apparatus,wherein the VfA pacing therapy apparatus comprises a tissue-piercingelectrode implantable from the triangle of Koch region of the rightatrium through the right atrial endocardium and central fibrous body todeliver the VfA pacing therapy to the left ventricle in the basal and/orseptal region of the left ventricular myocardium of the patient's heart.6. The system of claim 5, wherein the VfA paced settings comprises alocation of the at least one implantable electrode proximate the highposterior basal and/or septal area of the left ventricle of the patient.7. The system of claim 1, wherein the plurality of external electrodescomprises surface electrodes positioned in an array configured to belocated proximate skin of a torso of the patient.
 8. The system of claim1, wherein the paced EHI comprises a metric of electrical heterogeneity,wherein the determining whether the one or more VfA paced settings forthe VfA pacing therapy are acceptable comprises determining that the oneor more VfA paced settings are acceptable if the metric of electricalheterogeneity is less than or equal to a threshold.
 9. The system ofclaim 1, wherein the determining whether the one or more VfA pacedsettings for the VfA pacing therapy are acceptable comprises: generatingbaseline EHI from the monitored electrical activity without delivery ofthe VfA pacing therapy; comparing the baseline EHI to the paced EHI; anddetermining that the one or more VfA paced settings are acceptable basedon the comparison of the baseline EHI to the paced EHI.
 10. The systemof claim 1, wherein the electrical heterogeneity information comprisesat least one metric of electrical heterogeneity, wherein the at leastone metric of electrical heterogeneity comprises anterior-septalactivation times (ASAT), wherein ASAT comprises activation timesmonitored from external electrodes of the plurality of externalelectrodes that correspond to the anterior-septal region of the heart ofthe patient.
 11. The system of claim 1, wherein the electricalheterogeneity information comprises at least one metric of electricalheterogeneity, wherein the at least one metric of electricalheterogeneity comprises at least one of anterior-septal activation times(ASAT), a standard deviation of activation times (SDAT), a compositeleft ventricular activation time (LVAT), and a composite rightventricular activation time (RVAT).
 12. The system of claim 1, whereinthe computing apparatus is further configured to adjust the one or moreVfA paced settings for the VfA pacing therapy based on whether the VfApacing therapy is acceptable; and wherein the adjusted one or more VfApaced settings is determined to be acceptable in response to the VfApacing therapy correcting a bundle branch block (BBB).
 13. The system ofclaim 1, wherein the computing apparatus is further configured to adjustthe one or more VfA paced settings for the VfA pacing therapy based onwhether the VfA pacing therapy is acceptable; and wherein the adjustedone or more VfA paced settings is determined to be acceptable inresponse to the VfA pacing therapy completely engaging a Purkinje systemof the heart of the patient.
 14. A method comprising: monitoringelectrical activity from tissue of a patient using a plurality ofexternal electrodes; generating paced electrical heterogeneityinformation (EHI) based on the monitored electrical activity duringdelivery of ventricle from atrium (VfA) pacing therapy at one or moreVfA paced settings, wherein the paced EHI is representative of at leastone of mechanical cardiac functionality and electrical cardiacfunctionality; and determining whether the one or more VfA pacedsettings for the VfA pacing therapy are acceptable based on the pacedEHI.
 15. The method of claim 14, wherein the one or more VfA pacedsettings comprise at least one of a voltage, a pulse width, timing of aV-pacing relative to intrinsic or paced atrial timing, and pacing rate.16. The method of claim 14, wherein the one or more VfA paced settingscomprises a location of at least one implantable electrode wherein thelocation comprises at least one of depth and angle.
 17. The method ofclaim 14, wherein the one or more VfA paced settings comprises at leastone of a pacing polarity, a pacing vector, and a number of pacingelectrodes used.
 18. The method of claim 14, wherein the delivery of theVfA pacing therapy is performed by a VfA pacing therapy apparatus,wherein the VfA pacing therapy apparatus comprises a tissue-piercingelectrode implantable from the triangle of Koch region of the rightatrium through the right atrial endocardium and central fibrous body todeliver the VfA pacing therapy to the left ventricle in the basal and/orseptal region of the left ventricular myocardium of the patient.
 19. Themethod of claim 18, wherein the VfA paced settings comprises a locationof the at least one implantable electrode proximate the high posteriorbasal and/or septal area of the left ventricle of the patient.
 20. Themethod of claim 14, wherein the plurality of external electrodescomprises surface electrodes positioned in an array configured to belocated proximate skin of a torso of the patient.
 21. The method ofclaim 14, wherein the paced EHI comprises a metric of electricalheterogeneity, wherein the determining whether the one or more VfA pacedsettings for the VfA pacing therapy are acceptable comprises determiningthat the one or more VfA paced settings are acceptable if the metric ofelectrical heterogeneity is less than or equal to a threshold.
 22. Themethod of claim 14, wherein the determining whether the one or more VfApaced settings for the VfA pacing therapy are acceptable comprises:generating baseline EHI from the monitored electrical activity withoutdelivery of the VfA pacing therapy; comparing the baseline EHI to thepaced EHI; and determining that the one or more VfA paced settings areacceptable based on the comparison of the baseline EHI to the paced EHI.23. The method of claim 14, wherein the electrical heterogeneityinformation comprises at least one metric of electrical heterogeneity,wherein the at least one metric of electrical heterogeneity comprisesanterior-septal activation times (ASAT), wherein ASAT comprisesactivation times monitored from external electrodes of the plurality ofexternal electrodes that correspond to the anterior-septal region of theheart of the patient.
 24. The method of claim 14, wherein the electricalheterogeneity information comprises at least one metric of electricalheterogeneity, wherein the at least one metric of electricalheterogeneity comprises at least one of anterior-septal activation times(ASAT), a standard deviation of activation times (SDAT), a compositeleft ventricular activation time (LVAT), and a composite rightventricular activation time (RVAT).
 25. The method of claim 14, furthercomprising adjusting the one or more VfA paced settings for the VfApacing therapy based on whether the VfA pacing therapy is acceptable;and wherein the adjusted one or more VfA paced settings is determined tobe acceptable in response to the VfA pacing therapy correcting a bundlebranch block (BBB).
 26. The method of claim 14, wherein the computingapparatus is further configured to adjust the one or more VfA pacedsettings for the VfA pacing therapy based on whether the VfA pacingtherapy is acceptable; and wherein the adjusted one or more VfA pacedsettings is determined to be acceptable in response to the VfA pacingtherapy completely engaging a Purkinje system of the heart of thepatient.
 27. A system comprising: electrode apparatus comprising aplurality of external electrodes to monitor electrical activity fromtissue of a patient; and computing apparatus comprising processingcircuitry and coupled to the electrode apparatus and configured to:monitor electrical activity using the plurality of external electrodesduring delivery of ventricle from atrium (VfA) pacing therapy; generateelectrical heterogeneity information (EHI) during delivery of VfA pacingtherapy; determine whether a VfA paced setting for the VfA pacingtherapy is acceptable based on the EHI generated from the electricalactivity using the VfA paced setting; and adjust the paced setting forthe VfA pacing therapy based on whether the VfA pacing therapy isacceptable.